trac #14444 minor corrections

src/sage/combinat/cluster_algebra_quiver/mutation_type.py

@@ -272,7 +272,7 @@ def _check_special_BC_cases(dg, n, check_letter_list, check_twist_list,
         if not mut_type == 'unknown':
             mut_type, conn_verts = mut_type
     else:
-        # when conn_vert_list == False, the output of _connected_mutation_type _AAtildeD is simply 'unknown' or the mutation type.
+        # when conn_vert_list is False, the output of _connected_mutation_type _AAtildeD is simply 'unknown' or the mutation type.
         # no 'connecting vertices' need to be computed.
         mut_type = _connected_mutation_type_AAtildeD( dg, ret_conn_vert = False )
         conn_verts = []
@@ -1128,8 +1128,8 @@ def _connected_mutation_type_AAtildeD(dg, ret_conn_vert=False):
         else:
             long_cycle = [ cycle, ['A',n-1,1] ]
     # if we haven't found a "long_cycle", we are in finite type A
-    if long_cycle == False:
-        long_cycle = [ [], QuiverMutationType(['A',n]) ]
+    if not long_cycle:
+        long_cycle = [[], QuiverMutationType(['A', n])]
 
     # The 'connected vertices' are now computed.
     # Attention: 0-1-2 in type A_3 has connecting vertices 0 and 2, while in type D_3 it has connecting vertex 1;

src/sage/combinat/cluster_algebra_quiver/quiver_mutation_type.py

@@ -1491,7 +1491,7 @@ def __init__(self, letter, rank, twist=None):
 
         # type GaRo (Gale-Robinson)
         elif letter == 'GaRo':
-            if twist == None and type(rank) is list and len(rank) == 3 and all( rank[i] in ZZ for i in [0,1,2] ) and rank[0] > 0 and rank[1] > 0 and rank[2] > rank[1] and rank[2] <= rank[0]/2:
+            if twist is None and type(rank) is list and len(rank) == 3 and all( rank[i] in ZZ for i in [0, 1, 2] ) and rank[0] > 0 and rank[1] > 0 and rank[2] > rank[1] and rank[2] <= rank[0]/2:
                 N, r, s = rank
                 self._rank = N
                 self._digraph.allow_multiple_edges(True)
@@ -1577,7 +1577,7 @@ def __init__(self, letter, rank, twist=None):
 
         # type P1 (primitive period 1)
         elif letter == 'P1':
-            if twist == None and type(rank) is list and len(rank) ==2 and all( rank[i] in ZZ and rank[i] > 0 for i in [0,1]) and rank[1] <= rank[0]/2:
+            if twist is None and type(rank) is list and len(rank) ==2 and all( rank[i] in ZZ and rank[i] > 0 for i in [0,1]) and rank[1] <= rank[0]/2:
                 N, k = rank
                 self._rank = N
                 zero_again = False