Implemented to_file resolving #32 and use six in more places

to_file was implemented and tested, which leaves behind a file in the
tmp directory within functional/test/data.

In implementing this and using six.u, I found that I can use six.viewitems instead of
defining my own custom function.

.gitignore

@@ -54,3 +54,5 @@ docs/_build/
 
 # PyBuilder
 target/
+
+functional/test/data/tmp

functional/pipeline.py

@@ -4,6 +4,8 @@
 from operator import mul
 import collections
 from functools import reduce
+import builtins
+import six
 
 from .lineage import Lineage
 from .util import is_iterable, is_primitive, identity
@@ -1301,6 +1303,15 @@ def dict(self, default=None):
         """
         return self.to_dict(default=default)
 
+    def to_file(self, path, mode='w', buffering=-1, encoding=None, errors=None, newline=None):
+        """
+        Saves the sequence to a file by executing str(self) which becomes str(self.to_list())
+        """
+        # pylint: disable=too-many-arguments
+        with builtins.open(path, mode=mode, buffering=buffering, encoding=encoding, errors=errors,
+                           newline=newline) as output:
+            output.write(six.u(str(self)))
+
 
 def _wrap(value):
     """

functional/streams.py

@@ -4,9 +4,10 @@
 import re
 import csv as csvapi
 import json as jsonapi
+import six
 
 from .pipeline import Sequence
-from .util import is_primitive, LazyFile, dict_item_iter
+from .util import is_primitive, LazyFile
 
 
 def seq(*args):
@@ -153,7 +154,7 @@ def json(json_file):
     if isinstance(json_input, list):
         return seq(json_input)
     else:
-        return seq(dict_item_iter(json_input))
+        return seq(six.viewitems(json_input))
 
 
 seq.open = open

functional/test/test_streams.py

@@ -1,6 +1,6 @@
 import unittest
+import six
 from .. import seq
-from .. import util
 
 
 class TestStreams(unittest.TestCase):
@@ -42,7 +42,7 @@ def test_json(self):
         list_test_path = 'functional/test/data/test_list.json'
         dict_test_path = 'functional/test/data/test_dict.json'
         list_expect = [1, 2, 3, 4, 5]
-        dict_expect = list(util.dict_item_iter({u'a': 1, u'b': 2, u'c': 3}))
+        dict_expect = list(six.viewitems({u'a': 1, u'b': 2, u'c': 3}))
 
         result = seq.json(list_test_path).to_list()
         self.assertEqual(list_expect, result)
@@ -58,3 +58,11 @@ def test_json(self):
 
         with self.assertRaises(ValueError):
             seq.json(1)
+
+    def test_to_file(self):
+        tmp_path = 'functional/test/data/tmp/output.txt'
+        sequence = seq(1, 2, 3, 4)
+        sequence.to_file(tmp_path)
+        with open('functional/test/data/tmp/output.txt', 'r') as output:
+            self.assertEqual('[1, 2, 3, 4]', output.readlines()[0])
+

functional/transformations.py

@@ -7,8 +7,9 @@
 import collections
 from enum import Enum
 import types
+import six
 
-from .util import dict_item_iter, filterfalse
+from .util import filterfalse
 
 
 Transformation = collections.namedtuple(
@@ -253,7 +254,7 @@ def group_by_key_impl(sequence):
             result.get(element[0]).append(element[1])
         else:
             result[element[0]] = [element[1]]
-    return dict_item_iter(result)
+    return six.viewitems(result)
 
 
 def group_by_key_t():
@@ -281,7 +282,7 @@ def group_by_impl(func, sequence):
             result.get(func(element)).append(element)
         else:
             result[func(element)] = [element]
-    return dict_item_iter(result)
+    return six.viewitems(result)
 
 
 def group_by_t(func):
@@ -326,7 +327,7 @@ def inner_join_impl(other, sequence):
     for k in keys:
         if k in seq_kv and k in other_kv:
             result[k] = (seq_kv[k], other_kv[k])
-    return dict_item_iter(result)
+    return six.viewitems(result)
 
 
 def join_impl(other, join_type, sequence):
@@ -348,7 +349,7 @@ def join_impl(other, join_type, sequence):
     result = {}
     for k in keys:
         result[k] = (seq_kv.get(k), other_kv.get(k))
-    return dict_item_iter(result)
+    return six.viewitems(result)
 
 
 def join_t(other, join_type):

functional/util.py

@@ -6,15 +6,9 @@
 
 if six.PY2:
     from itertools import ifilterfalse as filterfalse
-
-    def dict_item_iter(dictionary):
-        return dictionary.viewitems()
 else:
     from itertools import filterfalse
 
-    def dict_item_iter(dictionary):
-        return dictionary.items()
-
 
 def is_primitive(val):
     """