PythonCharmers/python-future

__bool__ = __nonzero__ not detected

Open

#453 opened on May 2, 2019

View on GitHub
 (2 comments) (0 reactions) (0 assignees)Python (1,172 stars) (327 forks)batch import
0.19bugfuturize scripthelp wanted

Description

Code like:

class Foo(object):
    def __nonzero__(self):
        return True
    __bool__ = __nonzero__

results in

from builtins import object
class Foo(object):
    def __bool__(self):
        return True
    __bool__ = __nonzero__

and therefore raises in Python3:

  File "test.py", line 2, in <module>
    class Foo(object):
  File "test.py", line 5, in Foo
    __bool__ = __nonzero__
NameError: name '__nonzero__' is not defined

Contributor guide

Tech stack
python
Domain
developer experiencetooling
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Python 2 vs 3python future librarydunder methods
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
50
Research direction
Examine the futurize tool's translation logic for special methods, likely in the 'libfuturize' or 'future' source code. The bug occurs when nonzero is defined and bool is assigned as a class attribute; the tool incorrectly translates both. The fix should remove the assignment and convert nonzero to bool as the sole method. Review existing comments on the issue for additional context.