python - 创建元组的无意尾随逗号

Question

在 Python 中，像这样在尾部留下逗号当然不是 SyntaxError:

In [1]: x = 1 ,

In [2]: x
Out[2]: (1,)

In [3]: type(x)
Out[3]: tuple

但是，与此同时，如果结尾的逗号不小心，可能很难捕捉到这种“问题”，尤其是对于 Python 新手。

我在想，我们是否可以在 PyCharm 智能代码质量控制功能的帮助下，静态地尽早发现这种“问题”； mypy、pylint 或 flake8 静态代码分析工具。

或者，另一种想法是限制/突出显示在没有括号的情况下隐式创建一个项目元组。可能吗？

Answer 1

pylint已经检测到这是一个问题 ( as of version 1.7 )。

例如，这是我的tuple.py:

"""Module docstring to satisfy pylint"""

def main():
    """The main function"""
    thing = 1,
    print(type(thing))

if __name__ == "__main__":
    main()

$ pylint tuple.py
No config file found, using default configuration
************* Module tuple
R:  5, 0: Disallow trailing comma tuple (trailing-comma-tuple)

------------------------------------------------------------------
Your code has been rated at 8.00/10 (previous run: 8.00/10, +0.00)

$ pylint --help-msg trailing-comma-tuple
No config file found, using default configuration
:trailing-comma-tuple (R1707): *Disallow trailing comma tuple*
  In Python, a tuple is actually created by the comma symbol, not by the
  parentheses. Unfortunately, one can actually create a tuple by misplacing a
  trailing comma, which can lead to potential weird bugs in your code. You
  should always use parentheses explicitly for creating a tuple. This message
  belongs to the refactoring checker. It can't be emitted when using Python <
  3.0.