2to3 does not fix zip in some cases

[RobertG]

BPO	21628
Nosy	@benjaminp, @berkerpeksag, @stuarteberg
Superseder	bpo-20742: 2to3 zip fixer doesn't fix for loops.

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2014-06-02.11:15:08.742>
created_at = <Date 2014-06-01.17:27:53.399>
labels = ['expert-2to3']
title = '2to3 does not fix zip in some cases'
updated_at = <Date 2017-01-19.14:45:23.578>
user = 'https://bugs.python.org/RobertG'

bugs.python.org fields:

activity = <Date 2017-01-19.14:45:23.578>
actor = 'stuarteberg'
assignee = 'none'
closed = True
closed_date = <Date 2014-06-02.11:15:08.742>
closer = 'berker.peksag'
components = ['2to3 (2.x to 3.x conversion tool)']
creation = <Date 2014-06-01.17:27:53.399>
creator = 'RobertG'
dependencies = []
files = []
hgrepos = []
issue_num = 21628
keywords = []
message_count = 3.0
messages = ['219511', '219568', '285793']
nosy_count = 4.0
nosy_names = ['benjamin.peterson', 'berker.peksag', 'RobertG', 'stuarteberg']
pr_nums = []
priority = 'normal'
resolution = 'duplicate'
stage = 'resolved'
status = 'closed'
superseder = '20742'
type = None
url = 'https://bugs.python.org/issue21628'
versions = ['Python 3.4']

[RobertG]

Consider this program

def foo(a,b):
	return min(zip(a,b)[2])

print foo(range(5), (0,9,-9))

With the default options, 2to3 rewrites this as

def foo(a,b):
	return min(zip(a,b)[2])

print(foo(list(range(5)), (0,9,-9)))

For some reason, 2to3 fails to wrap the call to zip in a list, even though the 2to3 documentation says that there is a fixer which does this. Obviously, the generated code will not work in Python 3 since you can't subscript an iterator.

[berkerpeksag]

This is a duplicate of bpo-20742.

[stuarteberg]

Already closed, but FWIW, I think this was incorrectly marked as a duplicate. bpo-20742 discusses a different issue related to lib2to3 and zip.

Meanwhile, this issue has been raised again in 28837, so I will continue the discussion there. (I have a patch.)