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2to3 zip fixer doesn't fix for loops. #64941
Description
| BPO | 20742 |
|---|---|
| Nosy | @benjaminp, @drj11 |
| Superseder |
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 2021-10-20.22:45:21.073>
created_at = <Date 2014-02-23.11:11:47.707>
labels = ['type-bug', 'expert-2to3']
title = "2to3 zip fixer doesn't fix for loops."
updated_at = <Date 2021-10-20.22:45:21.073>
user = 'https://github.com/drj11'bugs.python.org fields:
activity = <Date 2021-10-20.22:45:21.073>
actor = 'iritkatriel'
assignee = 'none'
closed = True
closed_date = <Date 2021-10-20.22:45:21.073>
closer = 'iritkatriel'
components = ['2to3 (2.x to 3.x conversion tool)']
creation = <Date 2014-02-23.11:11:47.707>
creator = 'drj'
dependencies = []
files = []
hgrepos = []
issue_num = 20742
keywords = []
message_count = 3.0
messages = ['211989', '211991', '227772']
nosy_count = 4.0
nosy_names = ['peter.otten', 'benjamin.peterson', 'drj', 'RobertG']
pr_nums = []
priority = 'normal'
resolution = 'duplicate'
stage = 'resolved'
status = 'closed'
superseder = '45544'
type = 'behavior'
url = 'https://bugs.python.org/issue20742'
versions = ['Python 2.7', 'Python 3.4', 'Python 3.5']
Activity
drj11 commentedon Feb 23, 2014
Consider the following code:
2to3 does not convert the zip in this code to list(zip(...)); it does not change this code at all.
That can be an (obscure) bug because the zip in Python 2 has different semantics from the zip in Python 3.
The output of this program
is different in Python 2 and Python 3 (when converted with 2to3, which doesn't change the program).
In Python 2 the output is:
ababA##
In Python 3 the output is:
ab#ab#A
Obviously this example is somewhat contrived, but I have a non-contrived example involving decoding PNG images (if anyone is interested).
peterotten commentedon Feb 23, 2014
Hm, I would expect that in 99 times out of 100 the extra list(...) would be removed in a manual step following the automated conversion.
I'd really like to see the non-contrived example with a justified use of this evil side effect ;)
RobertG commentedon Sep 28, 2014
As far as a non contrived example, see http://bugs.python.org/issue21628, which was marked as a duplicate of this bug.
This bug is the main thing preventing me from using 2to3, so I think it is a real issue.