Resolves #53 by fixing the behavior of zip_with_index

Author: EntilZha

CHANGELOG.md

@@ -11,6 +11,9 @@
 ### Bug Fixes
 * Fixed case where `_wrap` is changing named tuples to arrays when it should preserve them
 * Fixed documentation on `to_file` which incorrectly copied from `seq.open` delimiter parameter
+* Fixed `Sequence.zip_with_index` behavior. used to mimic `enumerate` by zipping on the left size
+while scala and spark do zip on the right side. This introduces different behavior and more flexible
+behavior in combination with `enumerate` A start parameter was also added like in `enumerate`
 
 ## Release 0.4.1
 Fix python 3 build error due to wheel installation of enum34. Package no longer depends on enum34

README.md

@@ -245,7 +245,7 @@ Function | Description | Type
 `inits()` | Returns consecutive inits of sequence | transformation
 `tails()` | Returns consecutive tails of sequence | transformation
 `zip(other)` | Zips the sequence with `other` | transformation
-`zip_with_index()` | Zips the sequence with the index starting at zero on the left side | transformation
+`zip_with_index(start=0)` | Zips the sequence with the index starting at `start` on the right side | transformation
 `enumerate(start=0)` | Zips the sequence with the index starting at `start` on the left side | transformation
 `inner_join(other)` | Returns inner join of sequence with other. Must be a sequence of `(key, value)` pairs | transformation
 `outer_join(other)` | Returns outer join of sequence with other. Must be a sequence of `(key, value)` pairs | transformation

functional/pipeline.py

@@ -1035,16 +1035,16 @@ def zip(self, sequence):
         """
         return self._transform(transformations.zip_t(sequence))
 
-    def zip_with_index(self):
+    def zip_with_index(self, start=0):
         """
-        Zips the sequence to its index, with the index being the first element of each tuple.
+        Zips the sequence to its index, with the index being the second element of each tuple.
 
         >>> seq(['a', 'b', 'c']).zip_with_index()
-        [(0, 'a'), (1, 'b'), (2, 'c')]
+        [('a', 0), ('b', 1), ('c', 2)]
 
         :return: sequence zipped to its index
         """
-        return self._transform(transformations.zip_with_index_t())
+        return self._transform(transformations.zip_with_index_t(start))
 
     def enumerate(self, start=0):
         """

functional/test/test_functional.py

@@ -636,10 +636,14 @@ def test_zip(self):
 
     def test_zip_with_index(self):
         l = [2, 3, 4]
-        e = [(0, 2), (1, 3), (2, 4)]
+        e = [(2, 0), (3, 1), (4, 2)]
         result = seq(l).zip_with_index()
         self.assertIteratorEqual(result, e)
         self.assert_type(result)
+        e = [(2, 5), (3, 6), (4, 7)]
+        result = seq(l).zip_with_index(5)
+        self.assertIteratorEqual(result, e)
+        self.assert_type(result)
 
     def test_to_list(self):
         l = [1, 2, 3, "abc", {1: 2}, {1, 2, 3}]

functional/transformations.py

@@ -2,7 +2,7 @@
 from __future__ import absolute_import
 
 from functools import reduce, partial
-from itertools import dropwhile, takewhile, islice
+from itertools import dropwhile, takewhile, islice, count
 import collections
 import types
 
@@ -281,14 +281,14 @@ def zip_t(zip_sequence):
     )
 
 
-def zip_with_index_t():
+def zip_with_index_t(start):
     """
     Transformation for Sequence.zip_with_index
     :return: transformation
     """
     return Transformation(
         'zip_with_index',
-        enumerate,
+        lambda sequence: zip(sequence, count(start=start)),
         None
     )