PythonCharmers/python-future

futurize `__bool__` not implemented for subclasses of dict

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#282 建立於 2017年5月5日

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 (0 留言) (0 反應) (0 負責人)Python (1,172 star) (327 fork)batch import
0.20bughelp wanted

描述

If a run futurize on python 2 code containing a subclass of the built in dict, e.g.

class A(dict):
    __nonzero__(self):
    return False

it is translated to

class A(dict):
    __bool__(self):
    return False

However, the __bool__ method is not called in python 2. Seems some other kind of trickery is needed.

For now I'm working around the issue by doing

class A(dict):
    __bool__(self):
    return False
    if sys.version_info[0] == 2:
        __nonzero__ = __bool__

貢獻者指南

技術棧
python
領域
toolingbackend
議題類型
bug
難度面向新貢獻者的預計實作難度，1 表示很小改動，5 表示專家級工作。
3
預計時間有經驗貢獻者完成調查、實作、測試並準備 pull request 的粗略時間範圍。
1-3 hours
活動狀態議題目前的可參與程度：新鮮、活躍、陳舊、阻塞或等待維護者輸入。
stale
清晰度議題是否清楚說明預期改動、驗收標準和下一步。
clear
前置要求
Python 2/3 compatibility conceptsfamiliarity with special methods
新手友善度1-100 的估計分數，表示該議題對首次貢獻者的友善程度。
45
研究方向
Investigate the futurize source code, likely in the `libfuturize` or `futurize` directory, for the transformation that converts ` nonzero ` to ` bool `. The issue indicates that ` bool ` is not called in Python 2 for dict subclasses. Examine the implementation and consider adding a fallback that also defines ` nonzero ` for Python 2 compatibility. No linked PRs or comments exist.