From 8fe2a8a3f50915dbf1d0cb6c052d0ec4ce33f123 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Fr=C3=A9d=C3=A9ric=20Chapoton?=
 <chapoton@math.univ-lyon1.fr>
Date: Fri, 3 Feb 2017 13:53:27 +0100
Subject: [PATCH] py3: get rid of .iteritems in combinat folder

---
 src/sage/combinat/combinat.py                 |  3 +-
 src/sage/combinat/combinatorial_algebra.py    | 11 ++++---
 .../combinat/crystals/monomial_crystals.py    | 33 ++++++++++---------
 src/sage/combinat/designs/block_design.py     |  7 ++--
 src/sage/combinat/designs/database.py         |  5 +--
 .../combinat/designs/difference_family.py     |  3 +-
 src/sage/combinat/designs/ext_rep.py          |  3 +-
 .../combinat/designs/incidence_structures.py  | 13 ++++----
 src/sage/combinat/designs/latin_squares.py    |  5 ++-
 .../combinat/designs/orthogonal_arrays.py     |  7 ++--
 src/sage/combinat/finite_state_machine.py     | 25 +++++++-------
 src/sage/combinat/free_module.py              | 11 ++++---
 src/sage/combinat/fully_packed_loop.py        |  5 ++-
 src/sage/combinat/k_tableau.py                |  6 +++-
 src/sage/combinat/ncsf_qsym/qsym.py           |  5 ++-
 src/sage/combinat/partition.py                |  3 +-
 src/sage/combinat/posets/lattices.py          |  5 ++-
 src/sage/combinat/posets/posets.py            |  5 +--
 .../combinat/root_system/ambient_space.py     |  5 ++-
 .../root_lattice_realization_algebras.py      |  5 ++-
 src/sage/combinat/root_system/type_folded.py  |  5 ++-
 .../combinat/root_system/type_reducible.py    |  5 ++-
 src/sage/combinat/sf/character.py             |  5 ++-
 src/sage/combinat/sf/classical.py             |  5 ++-
 src/sage/combinat/sf/kfpoly.py                | 19 ++++++-----
 src/sage/combinat/sf/monomial.py              | 12 ++++---
 src/sage/combinat/sf/sfa.py                   | 18 ++++++----
 src/sage/combinat/species/stream.py           |  7 ++--
 src/sage/combinat/subset.py                   |  3 +-
 src/sage/combinat/symmetric_group_algebra.py  |  9 ++---
 .../symmetric_group_representations.py        |  3 +-
 src/sage/combinat/tiling.py                   | 13 ++++----
 src/sage/combinat/words/morphism.py           | 19 ++++++-----
 src/sage/combinat/words/suffix_trees.py       |  3 +-
 34 files changed, 183 insertions(+), 108 deletions(-)

diff --git a/src/sage/combinat/combinat.py b/src/sage/combinat/combinat.py
index 8be46df17ff..fd345fc4b33 100644
--- a/src/sage/combinat/combinat.py
+++ b/src/sage/combinat/combinat.py
@@ -144,6 +144,7 @@
 #*****************************************************************************
 from __future__ import absolute_import
 
+import six
 from six.moves import range
 
 from sage.interfaces.all import maxima
@@ -2702,7 +2703,7 @@ def bell_polynomial(n, k):
     for p in Partitions(n, length=k):
         factorial_product = 1
         power_factorial_product = 1
-        for part, count in p.to_exp_dict().iteritems():
+        for part, count in six.iteritems(p.to_exp_dict()):
             factorial_product *= factorial(count)
             power_factorial_product *= factorial(part)**count
         coefficient = factorial(n) // (factorial_product * power_factorial_product)
diff --git a/src/sage/combinat/combinatorial_algebra.py b/src/sage/combinat/combinatorial_algebra.py
index 003ae8ac6a0..502331bc66e 100644
--- a/src/sage/combinat/combinatorial_algebra.py
+++ b/src/sage/combinat/combinatorial_algebra.py
@@ -65,6 +65,9 @@
 from sage.categories.all import AlgebrasWithBasis
 from sage.structure.element import Element
 
+import six
+
+
 # TODO: migrate this completely to the combinatorial free module + categories framework
 
 # for backward compatibility
@@ -299,8 +302,8 @@ def product(self, left, right):
 
         #Do the case where the user specifies how to multiply basis elements
         if hasattr(self, '_multiply_basis'):
-            for (left_m, left_c) in left._monomial_coefficients.iteritems():
-                for (right_m, right_c) in right._monomial_coefficients.iteritems():
+            for (left_m, left_c) in six.iteritems(left._monomial_coefficients):
+                for (right_m, right_c) in six.iteritems(right._monomial_coefficients):
                     res = self._multiply_basis(left_m, right_m)
                     coeffprod = left_c * right_c
                     #Handle the case where the user returns a dictionary
@@ -313,7 +316,7 @@ def product(self, left, right):
                         else:
                             z_elt[res] = z_elt.get(res, ABRzero) + coeffprod
                             continue
-                    for m, c in res.iteritems():
+                    for m, c in six.iteritems(res):
                         z_elt[m] = z_elt.get(m, ABRzero) + coeffprod * c
 
         #We assume that the user handles the multiplication correctly on
@@ -332,7 +335,7 @@ def product(self, left, right):
         BR = self.base_ring()
         zero = BR(0)
         del_list = []
-        for m, c in z_elt.iteritems():
+        for m, c in six.iteritems(z_elt):
             if c == zero:
                 del_list.append(m)
         for m in del_list:
diff --git a/src/sage/combinat/crystals/monomial_crystals.py b/src/sage/combinat/crystals/monomial_crystals.py
index d569bf296d3..5889a681b2f 100644
--- a/src/sage/combinat/crystals/monomial_crystals.py
+++ b/src/sage/combinat/crystals/monomial_crystals.py
@@ -112,6 +112,9 @@
 from sage.matrix.matrix import is_Matrix
 from sage.matrix.matrix_space import MatrixSpace
 
+import six
+
+
 class NakajimaMonomial(Element):
     r"""
     An element of the monomial crystal.
@@ -187,7 +190,7 @@ def _repr_Y(self):
         if not self._Y:
             return "1"
 
-        L = sorted(self._Y.iteritems(), key=lambda x: (x[0][0], x[0][1]))
+        L = sorted(six.iteritems(self._Y), key=lambda x: (x[0][0], x[0][1]))
         exp = lambda e: "^{}".format(e) if e != 1 else ""
         return ' '.join("Y({},{})".format(mon[0][0], mon[0][1]) + exp(mon[1])
                         for mon in L)
@@ -211,7 +214,7 @@ def _repr_A(self):
         if not Y and not self._A:
             return "1"
 
-        L = sorted(Y.iteritems(), key=lambda x: (x[0][0], x[0][1]))
+        L = sorted(six.iteritems(Y), key=lambda x: (x[0][0], x[0][1]))
         exp = lambda e: "^{}".format(e) if e != 1 else ""
         ret = ' '.join("Y({},{})".format(mon[0][0], mon[0][1]) + exp(mon[1])
                         for mon in L)
@@ -219,7 +222,7 @@ def _repr_A(self):
             return ret
         if Y:
             ret += ' '
-        L = sorted(self._A.iteritems(), key=lambda x: (x[0][0], x[0][1]))
+        L = sorted(six.iteritems(self._A), key=lambda x: (x[0][0], x[0][1]))
         return ret + ' '.join("A({},{})".format(mon[0][0], mon[0][1]) + exp(mon[1])
                               for mon in L)
 
@@ -233,7 +236,7 @@ def __hash__(self):
             4715601665014767730  # 64-bit
             -512614286           # 32-bit
         """
-        return hash(frozenset(tuple(self._Y.iteritems())))
+        return hash(frozenset(tuple(six.iteritems(self._Y))))
 
     def __eq__(self, other):
         r"""
@@ -310,7 +313,7 @@ def _latex_Y(self):
         if not self._Y:
             return "\\boldsymbol{1}"
 
-        L = sorted(self._Y.iteritems(), key=lambda x:(x[0][0],x[0][1]))
+        L = sorted(six.iteritems(self._Y), key=lambda x:(x[0][0],x[0][1]))
         return_str = ''
         for x in L:
             if x[1] != 1:
@@ -338,14 +341,14 @@ def _latex_A(self):
         if not Y and not self._A:
             return "\\boldsymbol{1}"
 
-        L = sorted(Y.iteritems(), key=lambda x:(x[0][0],x[0][1]))
+        L = sorted(six.iteritems(Y), key=lambda x:(x[0][0],x[0][1]))
         return_str = ''
         for x in L:
             if x[1] != 1:
                 return_str += "Y_{%s,%s}"%(x[0][0],x[0][1]) + "^{%s} "%x[1]
             else:
                 return_str += "Y_{%s,%s} "%(x[0][0],x[0][1])
-        L = sorted(self._A.iteritems(), key=lambda x:(x[0][0],x[0][1]))
+        L = sorted(six.iteritems(self._A), key=lambda x:(x[0][0],x[0][1]))
         for x in L:
             if x[1] != 1:
                 return_str += "A_{%s,%s}"%(x[0][0],x[0][1]) + "^{%s} "%x[1]
@@ -372,7 +375,7 @@ def _classical_weight(self):
         """
         P = self.parent().weight_lattice_realization()
         La = P.fundamental_weights()
-        return P(sum(v*La[k[0]] for k,v in self._Y.iteritems()))
+        return P(sum(v*La[k[0]] for k,v in six.iteritems(self._Y)))
 
     def weight_in_root_lattice(self):
         r"""
@@ -398,7 +401,7 @@ def weight_in_root_lattice(self):
         """
         Q = RootSystem(self.parent().cartan_type()).root_lattice()
         al = Q.simple_roots()
-        return Q.sum(e*al[k[0]] for k,e in self._A.iteritems())
+        return Q.sum(e*al[k[0]] for k,e in six.iteritems(self._A))
 
     def weight(self):
         r"""
@@ -476,7 +479,7 @@ def phi(self, i):
                 continue
             else:
                 d[(i,a)] = 0
-        S = sorted((x for x in d.iteritems() if x[0][0] == i), key=lambda x: x[0][1])
+        S = sorted((x for x in six.iteritems(d) if x[0][0] == i), key=lambda x: x[0][1])
         return max(sum(S[k][1] for k in range(s)) for s in range(1,len(S)+1))
 
     def _ke(self, i):
@@ -508,7 +511,7 @@ def _ke(self, i):
                 d[(i,a)] = 0
         total = ZZ.zero()
         L = []
-        S = sorted((x for x in d.iteritems() if x[0][0] == i), key=lambda x: x[0][1])
+        S = sorted((x for x in six.iteritems(d) if x[0][0] == i), key=lambda x: x[0][1])
         for var,exp in S:
             total += exp
             if total == phi:
@@ -541,7 +544,7 @@ def _kf(self, i):
                 continue
             else:
                 d[(i,a)] = 0
-        S = sorted((x for x in d.iteritems() if x[0][0] == i), key=lambda x: x[0][1])
+        S = sorted((x for x in six.iteritems(d) if x[0][0] == i), key=lambda x: x[0][1])
         sum = 0
         phi = self.phi(i)
         for var,exp in S:
@@ -611,7 +614,7 @@ def e(self, i):
             if cm[j_index,i-shift] != 0:
                 Aik[(j, ke+c)] = cm[j_index,i-shift]
         # Multiply by Aik
-        for key,value in Aik.iteritems():
+        for key,value in six.iteritems(Aik):
             if key in newdict:
                 if newdict[key] == -value: # The result would be a 0 exponent
                     del newdict[key]
@@ -660,7 +663,7 @@ def f(self, i):
             if cm[j_index,i-shift] != 0:
                 Aik[(j, kf+c)] = -cm[j_index,i-shift]
         # Multiply by Aik
-        for key,value in Aik.iteritems():
+        for key,value in six.iteritems(Aik):
             if key in newdict:
                 if newdict[key] == -value: # The result would be a 0 exponent
                     del newdict[key]
@@ -921,7 +924,7 @@ def _element_constructor_(self, Y=None, A=None):
             if ct.is_finite():
                 shift = 1
             Y = {}
-            for k,v in A.iteritems():
+            for k,v in six.iteritems(A):
                 Y[k] = Y.get(k, 0) + v
                 Y[(k[0],k[1]+1)] = Y.get((k[0],k[1]+1), 0) + v
                 for j_index,j in enumerate(I):
diff --git a/src/sage/combinat/designs/block_design.py b/src/sage/combinat/designs/block_design.py
index 70eb78ad53f..cfa672d5757 100644
--- a/src/sage/combinat/designs/block_design.py
+++ b/src/sage/combinat/designs/block_design.py
@@ -68,6 +68,9 @@
 from sage.matrix.matrix_space import MatrixSpace
 
 
+import six
+
+
 BlockDesign = IncidenceStructure
 
 ###  utility functions  -------------------------------------------------------
@@ -273,7 +276,7 @@ def ProjectiveGeometryDesign(n, d, F, algorithm=None, point_coordinates=True, ch
             blocks.append(b)
         B = BlockDesign(len(points), blocks, name="ProjectiveGeometryDesign", check=check)
         if point_coordinates:
-            B.relabel({i:p[0] for p,i in points.iteritems()})
+            B.relabel({i:p[0] for p,i in six.iteritems(points)})
 
     elif algorithm == "gap":   # Requires GAP's Design
         from sage.interfaces.gap import gap
@@ -870,7 +873,7 @@ def AffineGeometryDesign(n, d, F, point_coordinates=True, check=True):
     B = BlockDesign(len(points), blocks, name="AffineGeometryDesign", check=check)
 
     if point_coordinates:
-        rd = {i:p[0][1:] for p,i in points.iteritems()}
+        rd = {i:p[0][1:] for p,i in six.iteritems(points)}
         for v in rd.values(): v.set_immutable()
         B.relabel(rd)
 
diff --git a/src/sage/combinat/designs/database.py b/src/sage/combinat/designs/database.py
index 4b2128911f8..93e83448adc 100644
--- a/src/sage/combinat/designs/database.py
+++ b/src/sage/combinat/designs/database.py
@@ -47,6 +47,7 @@
 ---------
 """
 from __future__ import print_function, absolute_import
+import six
 from six.moves import range
 
 from sage.combinat.designs.orthogonal_arrays import (OA_from_quasi_difference_matrix,
@@ -1684,7 +1685,7 @@ def OA_10_469():
         blocks[len(B)].append(B)
 
     # Product of each symmetric design with the OA
-    for b_size,symmetric_design in blocks.iteritems():
+    for b_size,symmetric_design in six.iteritems(blocks):
         matrix = _reorder_matrix(symmetric_design)
         OA.extend([[B[xx] for xx in R]
                    for R in incomplete_orthogonal_array(9,b_size,[1]*b_size)
@@ -2694,7 +2695,7 @@ def QDM_57_9_1_1_8():
     (12,413) : ((0,1,436,546,977,467,242,3695,682,483,3026,461,1334),     _ref_Abel_v_12_t),
 }
 # Translate all V(m,t) into (mt+1,m+2;1,0;t)-QDM constructors
-for (m,t),(vec,source) in Vmt_vectors.iteritems():
+for (m,t),(vec,source) in six.iteritems(Vmt_vectors):
     n,k,lmbda,mu,u = (m*t+1,m+2,1,0,t)
     if not (n+u,lmbda) in QDM:
         QDM[n+u,lmbda] = {}
diff --git a/src/sage/combinat/designs/difference_family.py b/src/sage/combinat/designs/difference_family.py
index b76df57621c..b8881e3e369 100644
--- a/src/sage/combinat/designs/difference_family.py
+++ b/src/sage/combinat/designs/difference_family.py
@@ -51,6 +51,7 @@
 from __future__ import division, print_function, absolute_import
 
 from builtins import zip
+import six
 from six import itervalues
 from six.moves import range
 
@@ -1537,7 +1538,7 @@ def difference_family(v, k, l=1, existence=False, explain_construction=False, ch
         elif explain_construction:
             return "The database contains a ({},{},{})-difference family".format(v,k,l)
 
-        vv, blocks = next(DF[v,k,l].iteritems())
+        vv, blocks = next(six.iteritems(DF[v,k,l]))
 
         # Build the group
         from sage.rings.finite_rings.integer_mod_ring import Zmod
diff --git a/src/sage/combinat/designs/ext_rep.py b/src/sage/combinat/designs/ext_rep.py
index 3c187efece0..17930329a8e 100644
--- a/src/sage/combinat/designs/ext_rep.py
+++ b/src/sage/combinat/designs/ext_rep.py
@@ -43,6 +43,7 @@
 import sys
 
 # import compatible with py2 and py3
+import six
 from six.moves.urllib.request import urlopen
 from six import string_types
 
@@ -871,7 +872,7 @@ def _start_element(self, name, attrs):
         elif name == 'designs':
             pass # self.outf.write(' <%s>\n' % name)
         if self.in_item:
-            for k, v in attrs.iteritems():
+            for k, v in six.iteritems(attrs):
                 attrs[k] = _encode_attribute(v)
             new_node = (name, attrs, [])
             self.node_stack.append(new_node)
diff --git a/src/sage/combinat/designs/incidence_structures.py b/src/sage/combinat/designs/incidence_structures.py
index 6ecb026d15a..001d2181017 100644
--- a/src/sage/combinat/designs/incidence_structures.py
+++ b/src/sage/combinat/designs/incidence_structures.py
@@ -40,6 +40,7 @@
 #***************************************************************************
 from __future__ import print_function
 
+import six
 from six import itervalues
 from six.moves import range
 
@@ -483,8 +484,8 @@ def is_isomorphic(self, other, certificate=False):
 
         if A == B:
             if certificate:
-                B_canon_rev = {y:x for x,y in B_canon.iteritems()}
-                return {x:B_canon_rev[xint] for x,xint in A_canon.iteritems()}
+                B_canon_rev = {y:x for x,y in six.iteritems(B_canon)}
+                return {x:B_canon_rev[xint] for x,xint in six.iteritems(A_canon)}
             else:
                 return True
         else:
@@ -898,7 +899,7 @@ def degrees(self, size=None):
                 for s in combinations(b,size):
                     d[s]+=1
             if self._point_to_index:
-                return {tuple([self._points[x] for x in s]):v for s,v in d.iteritems()}
+                return {tuple([self._points[x] for x in s]):v for s,v in six.iteritems(d)}
             else:
                 return d
 
@@ -1426,7 +1427,7 @@ def packing(self, solver=None, verbose=0):
         p.solve(log=verbose)
 
         return [[self._points[x] for x in self._blocks[i]]
-                for i,v in p.get_values(b).iteritems() if v]
+                for i,v in six.iteritems(p.get_values(b)) if v]
 
     def is_t_design(self, t=None, v=None, k=None, l=None, return_parameters=False):
         r"""
@@ -1948,7 +1949,7 @@ def is_resolvable(self, certificate=False, solver=None, verbose=0, check=True):
                 else:
                     # each class is stored as the list of indices of its blocks
                     self._classes = [[] for _ in range(n_classes)]
-                    for (t,i),v in p.get_values(b).iteritems():
+                    for (t,i),v in six.iteritems(p.get_values(b)):
                         if v:
                             self._classes[t].append(self._blocks[i])
 
@@ -2060,7 +2061,7 @@ def coloring(self, k=None, solver=None, verbose=0):
 
         col = [[] for i in range(k)]
 
-        for (x,i),v in p.get_values(b).iteritems():
+        for (x,i),v in six.iteritems(p.get_values(b)):
             if v:
                 col[i].append(self._points[x])
 
diff --git a/src/sage/combinat/designs/latin_squares.py b/src/sage/combinat/designs/latin_squares.py
index 6dcadb67d3a..f9a14402558 100644
--- a/src/sage/combinat/designs/latin_squares.py
+++ b/src/sage/combinat/designs/latin_squares.py
@@ -128,6 +128,9 @@
 from sage.categories.sets_cat import EmptySetError
 from sage.misc.unknown import Unknown
 
+import six
+
+
 def are_mutually_orthogonal_latin_squares(l, verbose=False):
     r"""
     Check wether the list of matrices in ``l`` form mutually orthogonal latin
@@ -470,7 +473,7 @@ def latin_square_product(M,N,*others):
          for jj in range(n)}
 
     L = lambda i_j: i_j[0] * n + i_j[1]
-    D = {(L(c[0]),L(c[1])): L(v) for c,v in D.iteritems()}
+    D = {(L(c[0]),L(c[1])): L(v) for c,v in six.iteritems(D)}
     P = Matrix(D)
 
     if others:
diff --git a/src/sage/combinat/designs/orthogonal_arrays.py b/src/sage/combinat/designs/orthogonal_arrays.py
index 887f866cd98..d149722e4d1 100644
--- a/src/sage/combinat/designs/orthogonal_arrays.py
+++ b/src/sage/combinat/designs/orthogonal_arrays.py
@@ -58,6 +58,7 @@
 from __future__ import print_function, absolute_import
 
 from builtins import zip
+import six
 from six import itervalues
 from six.moves import range
 
@@ -1375,7 +1376,7 @@ def incomplete_orthogonal_array(k,n,holes,resolvable=False, existence=False):
 
     # From a quasi-difference matrix
     elif number_of_holes==1 and any(uu==sum_of_holes and mu<=1 and lmbda==1 and k<=kk+1 for (nn,lmbda,mu,uu),(kk,_) in QDM.get((n,1),{}).iteritems()):
-        for (nn,lmbda,mu,uu),(kk,f) in QDM[n,1].iteritems():
+        for (nn,lmbda,mu,uu),(kk,f) in six.iteritems(QDM[n,1]):
             if uu==sum_of_holes and mu<=1 and lmbda==1 and k<=kk+1:
                 break
         G,M = f()
@@ -1806,8 +1807,8 @@ def OA_from_quasi_difference_matrix(M,G,add_col=True,fill_hole=True):
 
     # A cache for addition in G
     G_sum = [[0]*Gn for _ in range(Gn)]
-    for x,i in G_to_int.iteritems():
-        for xx,ii in G_to_int.iteritems():
+    for x,i in six.iteritems(G_to_int):
+        for xx,ii in six.iteritems(G_to_int):
             G_sum[i][ii] = G_to_int[x+xx]
 
     # Convert M to integers
diff --git a/src/sage/combinat/finite_state_machine.py b/src/sage/combinat/finite_state_machine.py
index f366bce30ac..fa668d81c4b 100644
--- a/src/sage/combinat/finite_state_machine.py
+++ b/src/sage/combinat/finite_state_machine.py
@@ -931,6 +931,7 @@
 from __future__ import print_function
 
 from builtins import zip
+import six
 from six.moves import range
 
 from six import itervalues
@@ -2062,7 +2063,7 @@ def _epsilon_successors_(self, fsm=None):
         _epsilon_successors_dict_[self].remove([])  # delete starting state
         if not _epsilon_successors_dict_[self]:
             del _epsilon_successors_dict_[self]
-        for s, outputs in _epsilon_successors_dict_.iteritems():
+        for s, outputs in six.iteritems(_epsilon_successors_dict_):
             _epsilon_successors_dict_[s] = [t for t, _ in
                                             itertools.groupby(sorted(outputs))]
         return _epsilon_successors_dict_
@@ -3202,10 +3203,10 @@ def __init__(self,
         elif hasattr(data, 'iteritems'):
             # data is a dict (or something similar),
             # format: key = from_state, value = iterator of transitions
-            for (sf, iter_transitions) in data.iteritems():
+            for (sf, iter_transitions) in six.iteritems(data):
                 self.add_state(sf)
                 if hasattr(iter_transitions, 'iteritems'):
-                    for (st, transition) in iter_transitions.iteritems():
+                    for (st, transition) in six.iteritems(iter_transitions):
                         self.add_state(st)
                         if is_FSMTransition(transition):
                             self.add_transition(transition)
@@ -4955,7 +4956,7 @@ def key_function(s):
                 key=key_function
                 ))
 
-        for ((source, target), transitions) in adjacent.iteritems():
+        for ((source, target), transitions) in six.iteritems(adjacent):
             if len(transitions) > 0:
                 labels = []
                 for transition in transitions:
@@ -6582,14 +6583,14 @@ def _iter_process_simple_(self, iterator):
                                    "'simple' iterator cannot be used "
                                    "here." %
                                    (len(current),))
-            pos, states = next(current.iteritems())
+            pos, states = next(six.iteritems(current))
             if len(states) > 1:
                 raise RuntimeError("Process has branched "
                                    "(visiting %s states in branch). The "
                                    "'simple' iterator cannot be used "
                                    "here." %
                                    (len(states),))
-            state, branch = next(states.iteritems())
+            state, branch = next(six.iteritems(states))
             if len(branch.outputs) > 1:
                 raise RuntimeError("Process has branched. "
                                    "(%s different outputs in branch). The "
@@ -9839,7 +9840,7 @@ def find_final_word_out(state):
         # have been computed as it may not be permissible to stop at a
         # formerly non-final state unless a cycle has been completed.
 
-        for (state, position), final_word_out in cache.iteritems():
+        for (state, position), final_word_out in six.iteritems(cache):
             if position == 0 and final_word_out is not None:
                 state.is_final = True
                 state.final_word_out = final_word_out
@@ -11764,7 +11765,7 @@ def is_equivalent(self, other):
 
         B = other.minimization().relabeled()
         labels = {B.process(path)[1].label(): state.label()
-                  for (state, path) in address.iteritems()}
+                  for (state, path) in six.iteritems(address)}
         try:
             return A == B.relabeled(labels=labels)
         except KeyError:
@@ -14423,8 +14424,8 @@ def __repr__(self):
             """
             data = sorted(
                 (state, pos, tape_cache, outputs)
-                for pos, states in self.iteritems()
-                for state, (tape_cache, outputs) in states.iteritems())
+                for pos, states in six.iteritems(self)
+                for state, (tape_cache, outputs) in six.iteritems(states))
             branch = "branch" if len(data) == 1 else "branches"
             result = "process (%s %s)" % (len(data), branch)
             for s, sdata in itertools.groupby(data, lambda x: x[0]):
@@ -14702,7 +14703,7 @@ def _push_branches_(self, state, tape_cache, outputs):
                     'but output is written.' % (state,))
 
         for eps_state, eps_outputs in \
-                state._epsilon_successors_(self.fsm).iteritems():
+                six.iteritems(state._epsilon_successors_(self.fsm)):
             if eps_state == state:
                 continue
                 # "eps_state == state" means epsilon cycle
@@ -14903,7 +14904,7 @@ def step(current_state, input_tape, outputs):
             return
 
         states_dict = self._current_.pop(heapq.heappop(self._current_positions_))
-        for state, branch in states_dict.iteritems():
+        for state, branch in six.iteritems(states_dict):
             step(state, branch.tape_cache, branch.outputs)
 
         return self._current_
diff --git a/src/sage/combinat/free_module.py b/src/sage/combinat/free_module.py
index a83b0d57e84..83e0863b3bc 100644
--- a/src/sage/combinat/free_module.py
+++ b/src/sage/combinat/free_module.py
@@ -30,6 +30,9 @@
 from sage.typeset.ascii_art import AsciiArt, empty_ascii_art
 from sage.typeset.unicode_art import UnicodeArt, empty_unicode_art
 
+import six
+
+
 # TODO: move the content of this class to CombinatorialFreeModule.Element and ModulesWithBasis.Element
 class CombinatorialFreeModuleElement(Element):
     def __init__(self, M, x):
@@ -67,7 +70,7 @@ def __iter__(self):
             sage: [i for i in sorted(a)]
             [([2, 1], 1), ([3], 1)]
         """
-        return self._monomial_coefficients.iteritems()
+        return six.iteritems(self._monomial_coefficients)
 
     def __contains__(self, x):
         """
@@ -1650,7 +1653,7 @@ def from_vector(self, vector):
             True
         """
         cc = self.get_order()
-        return self._from_dict(dict( (cc[index], coeff) for (index,coeff) in vector.iteritems()))
+        return self._from_dict(dict( (cc[index], coeff) for (index,coeff) in six.iteritems(vector)))
 
     def __cmp__(self, other):
         """
@@ -1880,9 +1883,9 @@ def _from_dict(self, d, coerce=False, remove_zeros=True):
         assert isinstance(d, dict)
         if coerce:
             R = self.base_ring()
-            d = {key: R(coeff) for key,coeff in d.iteritems()}
+            d = {key: R(coeff) for key,coeff in six.iteritems(d)}
         if remove_zeros:
-            d = {key: coeff for key, coeff in d.iteritems() if coeff}
+            d = {key: coeff for key, coeff in six.iteritems(d) if coeff}
         return self.element_class( self, d )
 
 class CombinatorialFreeModule_Tensor(CombinatorialFreeModule):
diff --git a/src/sage/combinat/fully_packed_loop.py b/src/sage/combinat/fully_packed_loop.py
index 9d55f7b8d4f..7aa8fec36ff 100644
--- a/src/sage/combinat/fully_packed_loop.py
+++ b/src/sage/combinat/fully_packed_loop.py
@@ -22,6 +22,9 @@
 from sage.misc.lazy_attribute import lazy_attribute
 
 
+import six
+
+
 class FullyPackedLoop(Element):
     r"""
     A class for fully packed loops.
@@ -1112,7 +1115,7 @@ def _vertex_dictionary(self):
             for j in range(n):
                 vertices[(i, j)] = 0
 
-        for end, vertex in self._end_point_dictionary.iteritems():
+        for end, vertex in six.iteritems(self._end_point_dictionary):
             vertices[vertex] = end
 
         return vertices
diff --git a/src/sage/combinat/k_tableau.py b/src/sage/combinat/k_tableau.py
index 7b1449fc3d1..9cf77ae7569 100644
--- a/src/sage/combinat/k_tableau.py
+++ b/src/sage/combinat/k_tableau.py
@@ -1027,7 +1027,7 @@ def list_of_standard_cells(self):
             r = self[0].count(1) - i - 1
             for v in range(1,mu[i]):
                 D = self.dictionary_of_coordinates_at_residues(v+1)
-                new_D = {a:b for (a,b) in D.iteritems() if all(x not in already_used for x in b)}
+                new_D = {a:b for (a,b) in six.iteritems(D) if all(x not in already_used for x in b)}
                 r = (r - min([self.k+1 - (x-r)%(self.k+1) for x in new_D]))%(self.k+1)
                 standard_cells.append(new_D[r][-1])
                 already_used += new_D[r]
@@ -4649,4 +4649,8 @@ def intermediate_shapes(t):
 
 # Deprecations from trac:18555. July 2016
 from sage.misc.superseded import deprecated_function_alias
+
+import six
+
+
 StrongTableaux.global_options = deprecated_function_alias(18555, StrongTableaux.options)
diff --git a/src/sage/combinat/ncsf_qsym/qsym.py b/src/sage/combinat/ncsf_qsym/qsym.py
index 9e7ddce77e1..b40615f3c7b 100644
--- a/src/sage/combinat/ncsf_qsym/qsym.py
+++ b/src/sage/combinat/ncsf_qsym/qsym.py
@@ -86,6 +86,9 @@
 from sage.categories.morphism import SetMorphism
 from sage.categories.homset import Hom
 
+import six
+
+
 class QuasiSymmetricFunctions(UniqueRepresentation, Parent):
     r"""
     .. rubric:: The Hopf algebra of quasisymmetric functions.
@@ -674,7 +677,7 @@ def from_polynomial(self, f, check=True):
         assert self.base_ring() == f.base_ring()
         exponent_coefficient = f.dict()
         z = {}
-        for (e, c) in exponent_coefficient.iteritems():
+        for (e, c) in six.iteritems(exponent_coefficient):
             I = Compositions()([ei for ei in e if ei > 0])
             if I not in z:
                 z[I] = c
diff --git a/src/sage/combinat/partition.py b/src/sage/combinat/partition.py
index c36f656b9fa..98d82745b47 100644
--- a/src/sage/combinat/partition.py
+++ b/src/sage/combinat/partition.py
@@ -280,6 +280,7 @@
 #*****************************************************************************
 from __future__ import print_function, absolute_import
 
+import six
 from six.moves import range
 
 from sage.interfaces.all import gap
@@ -3199,7 +3200,7 @@ def centralizer_size(self, t=0, q=0):
             1
         """
         size = prod(i ** mi * factorial(mi)
-                    for i, mi in self.to_exp_dict().iteritems())
+                    for i, mi in six.iteritems(self.to_exp_dict()))
         if t or q:
             size *= prod((ZZ.one() - q ** j) / (ZZ.one() - t ** j)
                          for j in self)
diff --git a/src/sage/combinat/posets/lattices.py b/src/sage/combinat/posets/lattices.py
index cc23b405680..371fda91bc1 100644
--- a/src/sage/combinat/posets/lattices.py
+++ b/src/sage/combinat/posets/lattices.py
@@ -134,6 +134,9 @@
                                            JoinSemilatticeElement)
 from sage.combinat.posets.hasse_diagram import LatticeError
 
+import six
+
+
 ####################################################################################
 
 def MeetSemilattice(data=None, *args, **options):
@@ -1383,7 +1386,7 @@ def is_relatively_complemented(self, certificate=False):
 
         for e1 in range(n-1):
             C = Counter(flatten([H.neighbors_out(e2) for e2 in H.neighbors_out(e1)]))
-            for e3, c in C.iteritems():
+            for e3, c in six.iteritems(C):
                 if c == 1 and len(H.closed_interval(e1, e3)) == 3:
                     if not certificate:
                         return False
diff --git a/src/sage/combinat/posets/posets.py b/src/sage/combinat/posets/posets.py
index 31bf5c1a10a..9ee9d6291e5 100644
--- a/src/sage/combinat/posets/posets.py
+++ b/src/sage/combinat/posets/posets.py
@@ -254,6 +254,7 @@
 # python3
 from __future__ import division, print_function, absolute_import
 
+import six
 from six.moves import range
 from six import itervalues
 
@@ -3010,7 +3011,7 @@ def init_LP(k,cycles,inc_P):
 
             # We create the digraphs of all color classes
             linear_extensions = [hasse_diagram.copy() for i in range(k)]
-            for ((u,v),i),x in p.get_values(b).iteritems():
+            for ((u,v),i),x in six.iteritems(p.get_values(b)):
                 if x == 1:
                     linear_extensions[i].add_edge(u,v)
 
@@ -4932,7 +4933,7 @@ def canonical_label(self, algorithm=None):
         """
         canonical_label = self._hasse_diagram.canonical_label(certificate=True,
                                                               algorithm=algorithm)[1]
-        canonical_label = {self._elements[v]:i for v,i in canonical_label.iteritems()}
+        canonical_label = {self._elements[v]:i for v,i in six.iteritems(canonical_label)}
         return self.relabel(canonical_label)
 
     def with_linear_extension(self, linear_extension):
diff --git a/src/sage/combinat/root_system/ambient_space.py b/src/sage/combinat/root_system/ambient_space.py
index f90f1139daf..9cc64aa8c28 100644
--- a/src/sage/combinat/root_system/ambient_space.py
+++ b/src/sage/combinat/root_system/ambient_space.py
@@ -15,6 +15,9 @@
 from sage.rings.all import ZZ, QQ
 from sage.categories.homset import End
 
+import six
+
+
 class AmbientSpace(CombinatorialFreeModule):
     r"""
     Abstract class for ambient spaces
@@ -386,7 +389,7 @@ def inner_product(self, lambdacheck):
         lambdacheck_mc = lambdacheck._monomial_coefficients
 
         result = self.parent().base_ring().zero()
-        for t,c in lambdacheck_mc.iteritems():
+        for t,c in six.iteritems(lambdacheck_mc):
             if t not in self_mc:
                 continue
             result += c*self_mc[t]
diff --git a/src/sage/combinat/root_system/root_lattice_realization_algebras.py b/src/sage/combinat/root_system/root_lattice_realization_algebras.py
index 3f11d5f9627..7942b6de883 100644
--- a/src/sage/combinat/root_system/root_lattice_realization_algebras.py
+++ b/src/sage/combinat/root_system/root_lattice_realization_algebras.py
@@ -21,6 +21,9 @@
 from sage.modules.free_module_element import vector
 from sage.combinat.root_system.hecke_algebra_representation import HeckeAlgebraRepresentation
 
+import six
+
+
 class Algebras(AlgebrasCategory):
     """
     The category of group algebras of root lattice realizations.
@@ -116,7 +119,7 @@ def from_polynomial(self, p):
             .. TODO:: make this work for Laurent polynomials too
             """
             L = self.basis().keys()
-            return self.sum_of_terms((L.from_vector(vector(t)), c) for (t,c) in p.dict().iteritems())
+            return self.sum_of_terms((L.from_vector(vector(t)), c) for (t,c) in six.iteritems(p.dict()))
 
         @cached_method
         def divided_difference_on_basis(self, weight, i):
diff --git a/src/sage/combinat/root_system/type_folded.py b/src/sage/combinat/root_system/type_folded.py
index 3b758c06b5b..9da9a4a796f 100644
--- a/src/sage/combinat/root_system/type_folded.py
+++ b/src/sage/combinat/root_system/type_folded.py
@@ -19,6 +19,9 @@
 from sage.sets.family import Family
 from sage.combinat.root_system.cartan_type import CartanType
 
+import six
+
+
 class CartanTypeFolded(UniqueRepresentation, SageObject):
     r"""
     A Cartan type realized from a (Dynkin) diagram folding.
@@ -178,7 +181,7 @@ def __classcall_private__(cls, cartan_type, virtual, orbit):
         if isinstance(orbit, dict):
             i_set = cartan_type.index_set()
             orb = [None]*len(i_set)
-            for k,v in orbit.iteritems():
+            for k,v in six.iteritems(orbit):
                 orb[i_set.index(k)] = tuple(v)
             orbit = tuple(orb)
         else:
diff --git a/src/sage/combinat/root_system/type_reducible.py b/src/sage/combinat/root_system/type_reducible.py
index 8b19ead34ba..eb919335e74 100644
--- a/src/sage/combinat/root_system/type_reducible.py
+++ b/src/sage/combinat/root_system/type_reducible.py
@@ -20,6 +20,9 @@
 import sage.combinat.root_system as root_system
 from sage.structure.sage_object import SageObject
 
+import six
+
+
 class CartanType(SageObject, CartanType_abstract):
     r"""
     A class for reducible Cartan types.
@@ -83,7 +86,7 @@ def __init__(self, types):
         Internally, this relabelling is stored as a dictionary::
 
             sage: t = CartanType(["A",4], ["BC",5,2], ["C",3])
-            sage: sorted(t._index_relabelling.iteritems())
+            sage: sorted(six.iteritems(t._index_relabelling))
             [((0, 1), 1), ((0, 2), 2), ((0, 3), 3), ((0, 4), 4),
              ((1, 0), 5), ((1, 1), 6), ((1, 2), 7), ((1, 3), 8), ((1, 4), 9), ((1, 5), 10),
              ((2, 1), 11), ((2, 2), 12), ((2, 3), 13)]
diff --git a/src/sage/combinat/sf/character.py b/src/sage/combinat/sf/character.py
index 0f3cb7f57e8..75f19fc7b58 100644
--- a/src/sage/combinat/sf/character.py
+++ b/src/sage/combinat/sf/character.py
@@ -36,6 +36,9 @@
 from sage.functions.other import binomial
 from sage.rings.integer import Integer
 
+import six
+
+
 class generic_character(SFA_generic):
     def _my_key(self, la):
         r"""
@@ -428,7 +431,7 @@ def _b_power_gamma(self, gamma):
 
         """
         return self._p.prod( self._b_power_k_r(Integer(k),Integer(r))
-                             for (k,r) in gamma.to_exp_dict().iteritems() )
+                             for (k,r) in six.iteritems(gamma.to_exp_dict()) )
 
     def _self_to_power_on_basis(self, lam):
         r"""
diff --git a/src/sage/combinat/sf/classical.py b/src/sage/combinat/sf/classical.py
index 755cae8d72e..c0af8d5b6b1 100644
--- a/src/sage/combinat/sf/classical.py
+++ b/src/sage/combinat/sf/classical.py
@@ -34,6 +34,9 @@
 from . import jack
 from . import orthotriang
 
+import six
+
+
 ZZ = IntegerRing()
 QQ = RationalField()
 
@@ -234,7 +237,7 @@ def _element_constructor_(self, x):
                 raise TypeError("no coerce map from x's parent's base ring (= %s) to self's base ring (= %s)"%(PBR, self.base_ring()))
 
             z_elt = {}
-            for m, c in x._monomial_coefficients.iteritems():
+            for m, c in six.iteritems(x._monomial_coefficients):
                 n = sum(m)
                 P._m_cache(n)
                 for part in P._self_to_m_cache[n][m]:
diff --git a/src/sage/combinat/sf/kfpoly.py b/src/sage/combinat/sf/kfpoly.py
index ecf5072c3c8..6763e56a371 100644
--- a/src/sage/combinat/sf/kfpoly.py
+++ b/src/sage/combinat/sf/kfpoly.py
@@ -27,6 +27,9 @@
 from sage.rings.integer_ring import ZZ
 
 
+import six
+
+
 def KostkaFoulkesPolynomial(mu, nu, t=None):
     r"""
     Returns the Kostka-Foulkes polynomial `K_{\mu, \nu}(t)`.
@@ -130,41 +133,41 @@ def schur_to_hl(mu, t=None):
         sage: schur_to_hl([1,1,1])
         {[1, 1, 1]: 1}
         sage: a = schur_to_hl([2,1])
-        sage: for mc in sorted(a.iteritems()): print(mc)
+        sage: for mc in sorted(six.iteritems(a)): print(mc)
         ([1, 1, 1], t^2 + t)
         ([2, 1], 1)
         sage: a = schur_to_hl([3])
-        sage: for mc in sorted(a.iteritems()): print(mc)
+        sage: for mc in sorted(six.iteritems(a)): print(mc)
         ([1, 1, 1], t^3)
         ([2, 1], t)
         ([3], 1)
         sage: a = schur_to_hl([4])
-        sage: for mc in sorted(a.iteritems()): print(mc)
+        sage: for mc in sorted(six.iteritems(a)): print(mc)
         ([1, 1, 1, 1], t^6)
         ([2, 1, 1], t^3)
         ([2, 2], t^2)
         ([3, 1], t)
         ([4], 1)
         sage: a = schur_to_hl([3,1])
-        sage: for mc in sorted(a.iteritems()): print(mc)
+        sage: for mc in sorted(six.iteritems(a)): print(mc)
         ([1, 1, 1, 1], t^5 + t^4 + t^3)
         ([2, 1, 1], t^2 + t)
         ([2, 2], t)
         ([3, 1], 1)
         sage: a = schur_to_hl([2,2])
-        sage: for mc in sorted(a.iteritems()): print(mc)
+        sage: for mc in sorted(six.iteritems(a)): print(mc)
         ([1, 1, 1, 1], t^4 + t^2)
         ([2, 1, 1], t)
         ([2, 2], 1)
         sage: a = schur_to_hl([2,1,1])
-        sage: for mc in sorted(a.iteritems()): print(mc)
+        sage: for mc in sorted(six.iteritems(a)): print(mc)
         ([1, 1, 1, 1], t^3 + t^2 + t)
         ([2, 1, 1], 1)
         sage: a = schur_to_hl([1,1,1,1])
-        sage: for mc in sorted(a.iteritems()): print(mc)
+        sage: for mc in sorted(six.iteritems(a)): print(mc)
         ([1, 1, 1, 1], 1)
         sage: a = schur_to_hl([2,2,2])
-        sage: for mc in sorted(a.iteritems()): print(mc)
+        sage: for mc in sorted(six.iteritems(a)): print(mc)
         ([1, 1, 1, 1, 1, 1], t^9 + t^7 + t^6 + t^5 + t^3)
         ([2, 1, 1, 1, 1], t^4 + t^2)
         ([2, 2, 1, 1], t)
diff --git a/src/sage/combinat/sf/monomial.py b/src/sage/combinat/sf/monomial.py
index fbc4c1386c6..02c6f39e462 100644
--- a/src/sage/combinat/sf/monomial.py
+++ b/src/sage/combinat/sf/monomial.py
@@ -113,8 +113,8 @@ def _multiply(self, left, right):
         #    return symmetrica.mult_monomial_monomial(left, right)
 
         z_elt = {}
-        for (left_m, left_c) in left._monomial_coefficients.iteritems():
-            for (right_m, right_c) in right._monomial_coefficients.iteritems():
+        for (left_m, left_c) in six.iteritems(left._monomial_coefficients):
+            for (right_m, right_c) in six.iteritems(right._monomial_coefficients):
 
                 #Hack due to symmetrica crashing when both of the
                 #partitions are the empty partition
@@ -172,7 +172,7 @@ def from_polynomial(self, f, check=True):
         """
         assert self.base_ring() == f.base_ring()
         out = self.sum_of_terms((Partition(e), c)
-                                for (e,c) in f.dict().iteritems()
+                                for (e,c) in six.iteritems(f.dict())
                                 if tuple(sorted(e)) == tuple(reversed(e)))
         if check and out.expand(f.parent().ngens(),f.parent().gens()) != f:
             raise ValueError("%s is not a symmetric polynomial"%f)
@@ -223,7 +223,7 @@ def from_polynomial_exp(self, p):
         """
         assert self.base_ring() == p.parent().base_ring()
         return self.sum_of_terms((Partition(exp=monomial), coeff)
-                                 for (monomial, coeff) in p.dict().iteritems())
+                                 for (monomial, coeff) in six.iteritems(p.dict()))
 
     def antipode_by_coercion(self, element):
         r"""
@@ -302,4 +302,8 @@ def expand(self, n, alphabet='x'):
 
 # Backward compatibility for unpickling
 from sage.structure.sage_object import register_unpickle_override
+
+import six
+
+
 register_unpickle_override('sage.combinat.sf.monomial', 'SymmetricFunctionAlgebraElement_monomial',  SymmetricFunctionAlgebra_monomial.Element)
diff --git a/src/sage/combinat/sf/sfa.py b/src/sage/combinat/sf/sfa.py
index 43c6d810ef4..c62e860ea15 100644
--- a/src/sage/combinat/sf/sfa.py
+++ b/src/sage/combinat/sf/sfa.py
@@ -299,6 +299,10 @@ def is_SymmetricFunction(x):
 ## Bases categories
 
 from sage.categories.realizations import Category_realization_of_parent
+
+import six
+
+
 class SymmetricFunctionsBases(Category_realization_of_parent):
     r"""
     The category of bases of the ring of symmetric functions.
@@ -1624,7 +1628,7 @@ def _change_by_proportionality(self, x, function):
         """
         BR = self.base_ring()
         z_elt = {}
-        for m, c in x._monomial_coefficients.iteritems():
+        for m, c in six.iteritems(x._monomial_coefficients):
             coeff = function(m)
             z_elt[m] = BR( c*coeff )
         return self._from_dict(z_elt)
@@ -1709,7 +1713,7 @@ def _apply_multi_module_morphism(self, x, y, f, orthogonal=False):
         if orthogonal:
             # could check which of x and y has less terms
             # for mx, cx in x:
-            for mx, cx in x._monomial_coefficients.iteritems():
+            for mx, cx in six.iteritems(x._monomial_coefficients):
                 if mx not in y._monomial_coefficients:
                     continue
                 else:
@@ -1719,8 +1723,8 @@ def _apply_multi_module_morphism(self, x, y, f, orthogonal=False):
                 res += cx*cy*f(mx, mx)
             return res
         else:
-            for mx, cx in x._monomial_coefficients.iteritems():
-                for my, cy in y._monomial_coefficients.iteritems():
+            for mx, cx in six.iteritems(x._monomial_coefficients):
+                for my, cy in six.iteritems(y._monomial_coefficients):
                     res += cx*cy*f(mx,my)
             return res
 
@@ -1804,13 +1808,13 @@ def _from_cache(self, element, cache_function, cache_dict, **subs_dict):
         BR = self.base_ring()
         zero = BR.zero()
         z_elt = {}
-        for part, c in element.monomial_coefficients().iteritems():
+        for part, c in six.iteritems(element.monomial_coefficients()):
             if sum(part) not in cache_dict:
                 cache_function(sum(part))
             # Make sure it is a partition (for #13605), this is
             #   needed for the old kschur functions - TCS
             part = _Partitions(part)
-            for part2, c2 in cache_dict[sum(part)][part].iteritems():
+            for part2, c2 in six.iteritems(cache_dict[sum(part)][part]):
                 if hasattr(c2,'subs'): # c3 may be in the base ring
                     c3 = c*BR(c2.subs(**subs_dict))
                 else:
@@ -3066,7 +3070,7 @@ def inner_plethysm(self, x):
         cache = {}
         ip_pnu_g = parent._inner_plethysm_pnu_g
         return parent.sum( c*ip_pnu_g(p(x), cache, nu)
-                           for (nu, c) in p(self).monomial_coefficients().iteritems() )
+                           for (nu, c) in six.iteritems(p(self).monomial_coefficients()) )
 
 
     def omega(self):
diff --git a/src/sage/combinat/species/stream.py b/src/sage/combinat/species/stream.py
index 0f0414605f4..87df266e7a2 100644
--- a/src/sage/combinat/species/stream.py
+++ b/src/sage/combinat/species/stream.py
@@ -10,6 +10,9 @@
 import types
 from sage.structure.sage_object import SageObject
 
+import six
+
+
 def _integers_from(n):
     """
     Returns a generator for the integers starting at n.
@@ -133,7 +136,7 @@ def __init__(self, gen=None, const=None, func=None):
 
         ::
 
-            sage: list(sorted(s.__dict__.iteritems()))
+            sage: list(sorted(six.iteritems(s.__dict__)))
             [('_constant', 4),
              ('_gen', None),
              ('_last_index', 0),
@@ -143,7 +146,7 @@ def __init__(self, gen=None, const=None, func=None):
         ::
 
             sage: s = Stream(ZZ)
-            sage: list(sorted(s.__dict__.iteritems()))
+            sage: list(sorted(six.iteritems(s.__dict__)))
             [('_constant', None),
              ('_gen', <generator object at 0x...>),
              ('_last_index', -1),
diff --git a/src/sage/combinat/subset.py b/src/sage/combinat/subset.py
index 409701311cc..d00005c7923 100644
--- a/src/sage/combinat/subset.py
+++ b/src/sage/combinat/subset.py
@@ -28,6 +28,7 @@
 #*****************************************************************************
 from __future__ import print_function, absolute_import
 
+import six
 from six.moves import range
 import sage.misc.prandom as rnd
 import itertools
@@ -824,7 +825,7 @@ def dict_to_list(d):
         ['a', 'b', 'b', 'b']
     """
     l = []
-    for i,j in d.iteritems():
+    for i,j in six.iteritems(d):
         l.extend([i]*j)
     return l
 
diff --git a/src/sage/combinat/symmetric_group_algebra.py b/src/sage/combinat/symmetric_group_algebra.py
index abd78422aee..2affb7a91a0 100644
--- a/src/sage/combinat/symmetric_group_algebra.py
+++ b/src/sage/combinat/symmetric_group_algebra.py
@@ -25,6 +25,7 @@
 from sage.groups.perm_gps.permgroup_element import PermutationGroupElement
 import itertools
 from sage.combinat.permutation_cython import (left_action_same_n, right_action_same_n)
+import six
 
 # TODO: Remove this function and replace it with the class
 # TODO: Create parents for other bases (such as the seminormal basis)
@@ -701,7 +702,7 @@ def retract_plain(self, f, m):
         I = RSm.group()
         pairs = []
         P = Permutations(self.n)
-        for (p, coeff) in f.monomial_coefficients().iteritems():
+        for (p, coeff) in six.iteritems(f.monomial_coefficients()):
             p_ret = P(p).retract_plain(m)
             if p_ret is not None:
                 pairs.append((I(p_ret), coeff))
@@ -767,7 +768,7 @@ def retract_direct_product(self, f, m):
         I = RSm.group()
         dct = {}
         P = Permutations(self.n)
-        for (p, coeff) in f.monomial_coefficients().iteritems():
+        for (p, coeff) in six.iteritems(f.monomial_coefficients()):
             p_ret = P(p).retract_direct_product(m)
             if p_ret is not None:
                 p_ret = I(p_ret)
@@ -830,7 +831,7 @@ def retract_okounkov_vershik(self, f, m):
         I = RSm.group()
         dct = {}
         P = Permutations(self.n)
-        for (p, coeff) in f.monomial_coefficients().iteritems():
+        for (p, coeff) in six.iteritems(f.monomial_coefficients()):
             p_ret = I(P(p).retract_okounkov_vershik(m))
             if not p_ret in dct:
                 dct[p_ret] = coeff
@@ -1679,7 +1680,7 @@ def epsilon_ik(self, itab, ktab, star=0, mult='l2r'):
         I = self._indices
         z_elts = {}
         epik = epsilon_ik(it, kt, star=star)
-        for m,c in epik._monomial_coefficients.iteritems():
+        for m,c in six.iteritems(epik._monomial_coefficients):
             z_elts[I(m)] = BR(c)
         z = self._from_dict(z_elts)
 
diff --git a/src/sage/combinat/symmetric_group_representations.py b/src/sage/combinat/symmetric_group_representations.py
index 38331b0064c..8b6371da675 100644
--- a/src/sage/combinat/symmetric_group_representations.py
+++ b/src/sage/combinat/symmetric_group_representations.py
@@ -28,6 +28,7 @@
 #                  http://www.gnu.org/licenses/
 #*****************************************************************************
 from __future__ import print_function
+import six
 from six.moves import range
 
 from sage.symbolic.ring import SR
@@ -569,7 +570,7 @@ def _word_dict(self):
              (2, 0, 1, -1, 0): (2, 4, 1, 3, 5)}
         """
         word_dict = {}
-        for (v,t) in self._tableau_dict.iteritems():
+        for (v,t) in six.iteritems(self._tableau_dict):
             word_dict[v] = sum(reversed(t), ())
         return word_dict
 
diff --git a/src/sage/combinat/tiling.py b/src/sage/combinat/tiling.py
index 165a6e60509..b6fafeb3907 100644
--- a/src/sage/combinat/tiling.py
+++ b/src/sage/combinat/tiling.py
@@ -222,6 +222,7 @@
 from __future__ import division
 
 from builtins import zip
+import six
 from six.moves import range
 
 import itertools
@@ -997,10 +998,10 @@ def boundary(self):
             vertical[(x+1, y)] -= 1
         edges = []
         h = 0.5
-        for (x, y), coeff in horizontal.iteritems():
+        for (x, y), coeff in six.iteritems(horizontal):
             if coeff != 0:
                 edges.append(((x-h, y-h), (x+h, y-h)))
-        for (x, y), coeff in vertical.iteritems():
+        for (x, y), coeff in six.iteritems(vertical):
             if coeff != 0:
                 edges.append(((x-h, y-h), (x-h, y+h)))
         return edges
@@ -1277,7 +1278,7 @@ def coord_to_int_dict(self):
             sage: r = Polyomino([(0,0,0), (0,0,1), (0,0,2)])
             sage: T = TilingSolver([p,q,r], box=(1,1,6))
             sage: A = T.coord_to_int_dict()
-            sage: sorted(A.iteritems())
+            sage: sorted(six.iteritems(A))
             [((0, 0, 0), 3), ((0, 0, 1), 4), ((0, 0, 2), 5), ((0, 0, 3), 6), ((0, 0, 4), 7), ((0, 0, 5), 8)]
 
         Reusable pieces::
@@ -1286,7 +1287,7 @@ def coord_to_int_dict(self):
             sage: q = Polyomino([(0,0), (0,1), (1,0), (1,1)])
             sage: T = TilingSolver([p,q], box=[3,2], reusable=True)
             sage: B = T.coord_to_int_dict()
-            sage: sorted(B.iteritems())
+            sage: sorted(six.iteritems(B))
             [((0, 0), 0), ((0, 1), 1), ((1, 0), 2), ((1, 1), 3), ((2, 0), 4), ((2, 1), 5)]
         """
         if self._reusable:
@@ -1309,7 +1310,7 @@ def int_to_coord_dict(self):
             sage: r = Polyomino([(0,0,0), (0,0,1), (0,0,2)])
             sage: T = TilingSolver([p,q,r], box=(1,1,6))
             sage: B = T.int_to_coord_dict()
-            sage: sorted(B.iteritems())
+            sage: sorted(six.iteritems(B))
             [(3, (0, 0, 0)), (4, (0, 0, 1)), (5, (0, 0, 2)), (6, (0, 0, 3)), (7, (0, 0, 4)), (8, (0, 0, 5))]
 
         Reusable pieces::
@@ -1319,7 +1320,7 @@ def int_to_coord_dict(self):
             sage: q = Polyomino([(0,0), (0,1), (1,0), (1,1)])
             sage: T = TilingSolver([p,q], box=[3,2], reusable=True)
             sage: B = T.int_to_coord_dict()
-            sage: sorted(B.iteritems())
+            sage: sorted(six.iteritems(B))
             [(0, (0, 0)), (1, (0, 1)), (2, (1, 0)), (3, (1, 1)), (4, (2, 0)), (5, (2, 1))]
 
         TESTS:
diff --git a/src/sage/combinat/words/morphism.py b/src/sage/combinat/words/morphism.py
index 99ff039d9af..87b1afc7d16 100644
--- a/src/sage/combinat/words/morphism.py
+++ b/src/sage/combinat/words/morphism.py
@@ -103,6 +103,7 @@
 from sage.matrix.constructor import Matrix
 from sage.combinat.words.word import FiniteWord_class
 from sage.combinat.words.words import FiniteWords, FiniteOrInfiniteWords
+import six
 
 def get_cycles(f, domain=None):
     r"""
@@ -387,7 +388,7 @@ def __init__(self, data, domain=None, codomain=None):
             self._morph = {}
 
             dom_alph = list()
-            for (key,val) in data.iteritems():
+            for (key,val) in six.iteritems(data):
                 dom_alph.append(key)
                 if val in codomain.alphabet():
                     self._morph[key] = codomain([val])
@@ -468,7 +469,7 @@ def _build_codomain(self, data):
             Finite words over {0, 1, 2}
         """
         codom_alphabet = set()
-        for key,val in data.iteritems():
+        for key,val in six.iteritems(data):
             try:
                 it = iter(val)
             except Exception:
@@ -484,7 +485,7 @@ def __hash__(self):
             sage: hash(WordMorphism('a->ab,b->ba')) # random
             7211091143079804375
         """
-        return hash(tuple((k,v) for k,v in self._morph.iteritems())) ^ hash(self._codomain)
+        return hash(tuple((k,v) for k,v in six.iteritems(self._morph))) ^ hash(self._codomain)
 
     def __eq__(self, other):
         r"""
@@ -597,7 +598,7 @@ def __str__(self):
             sage: str(s)
             'a->ab, b->ba'
         """
-        L = [str(lettre) + '->' + image.string_rep() for lettre,image in self._morph.iteritems()]
+        L = [str(lettre) + '->' + image.string_rep() for lettre,image in six.iteritems(self._morph)]
         return ', '.join(sorted(L))
 
     def __call__(self, w, order=1, datatype='iter'):
@@ -772,7 +773,7 @@ def __call__(self, w, order=1, datatype='iter'):
                 length = 'finite'
             elif isinstance(w, FiniteWord_class):
                 #Is it really a good thing to precompute the length?
-                length = sum(self._morph[a].length() * b for (a,b) in w.evaluation_dict().iteritems())
+                length = sum(self._morph[a].length() * b for (a,b) in six.iteritems(w.evaluation_dict()))
             elif hasattr(w, '__iter__'):
                 length = Infinity
                 datatype = 'iter'
@@ -947,7 +948,7 @@ def __mul__(self, other):
             sage: m * WordMorphism('')
             WordMorphism:
         """
-        return WordMorphism(dict((key, self(w)) for (key, w) in other._morph.iteritems()), codomain=self.codomain())
+        return WordMorphism(dict((key, self(w)) for (key, w) in six.iteritems(other._morph)), codomain=self.codomain())
 
     def __pow__(self, exp):
         r"""
@@ -1052,7 +1053,7 @@ def extend_by(self, other):
             raise TypeError("other (=%s) is not a WordMorphism"%other)
 
         nv = dict(other._morph)
-        for k,v in self._morph.iteritems():
+        for k,v in six.iteritems(self._morph):
             nv[k] = v
         return WordMorphism(nv)
 
@@ -1273,7 +1274,7 @@ def reversal(self):
             sage: WordMorphism('a->ab,b->a').reversal()
             WordMorphism: a->ba, b->a
         """
-        return WordMorphism(dict((key, w.reversal()) for (key, w) in self._morph.iteritems()),codomain=self._codomain)
+        return WordMorphism(dict((key, w.reversal()) for (key, w) in six.iteritems(self._morph)),codomain=self._codomain)
 
     def is_empty(self):
         r"""
@@ -2031,7 +2032,7 @@ def conjugate(self, pos):
             sage: m.conjugate(2)
             WordMorphism: a->cdeab, b->zxy
         """
-        return WordMorphism(dict((key, w.conjugate(pos)) for (key, w) in self._morph.iteritems()))
+        return WordMorphism(dict((key, w.conjugate(pos)) for (key, w) in six.iteritems(self._morph)))
 
     def has_left_conjugate(self):
         r"""
diff --git a/src/sage/combinat/words/suffix_trees.py b/src/sage/combinat/words/suffix_trees.py
index 173264256e5..cd06c4eabaf 100644
--- a/src/sage/combinat/words/suffix_trees.py
+++ b/src/sage/combinat/words/suffix_trees.py
@@ -11,6 +11,7 @@
 #                  http://www.gnu.org/licenses/
 #*****************************************************************************
 
+import six
 from six import iteritems
 
 from sage.structure.sage_object import SageObject
@@ -278,7 +279,7 @@ def transition_function(self, node, word):
             sage: w = Words([0,1])([0,1,0,1,1])
             sage: t = SuffixTrie(w)
             sage: [t.transition_function(u,letter) == v \
-                    for ((u,letter),v) in t._transition_function.iteritems()] \
+                    for ((u,letter),v) in six.iteritems(t._transition_function)] \
                     == [True] * len(t._transition_function)
             True
         """