python - 如何通过warnings.warn抑制源上下文的打印？

Question

如果我将以下代码段放入文件中annoying.py：

import warnings
message = 'I know!  How about if we are just maximally annoying?!'
warnings.warn(message)

...并在 Unix shell 中运行它，这就是我得到的：

% python annoying.py
annoying.py:3: UserWarning: I know!  How about if we are just maximally annoying?!
  warnings.warn(message)

（我使用 Python 3.7.3 和 2.7.16 得到相同的输出。）

我只想打印此输出的第一行。

关于我正在做的事情，第二行只会增加视觉上分散注意力的混乱。（当有很多警告时，这种无缘无故的混乱变得特别成问题。）

如何抑制第二条/杂乱线？

标签： pythonwarnings

Answer 1

从warnings.py源代码看来， msg.line 控制是否需要打印额外的行。可以猴子修补 WarningMessage 的初始化，这样 self.line 是 "" 而不是 None 如下所示

import warnings

#modify the __init__ so that self.line = "" instead of None
def new_init(self, message, category, filename, lineno, file=None,
                 line=None, source=None):
        self.message = message
        self.category = category
        self.filename = filename
        self.lineno = lineno
        self.file = file
        self.line = ""
        self.source = source
        self._category_name = category.__name__ if category else None

warnings.WarningMessage.__init__ = new_init

message = 'I know!  How about if we are just maximally annoying?!'
warnings.warn(message)

这导致：

annoying.py:19: UserWarning: I know!  How about if we are just maximally annoying?!

另一种 hacky 方法可能是使用 -W 选项将警告作为错误出现：

% python -Werror::UserWarning annoying.py

如果您有以下烦恼.py

import warnings
message = 'I know!  How about if we are just maximally annoying?!'
try:
    warnings.warn(message)
except Exception as error:
    print(error) 

结果是

I know!  How about if we are just maximally annoying?!

要获取文件名、行号、警告类型和警告消息，我必须执行以下操作

import warnings
import sys, os
message = 'I know!  How about if we are just maximally annoying?!'
try:
    warnings.warn(message)
except Exception as error:
    exc_type, exc_obj, exc_tb = sys.exc_info()
    fname = os.path.split(exc_tb.tb_frame.f_code.co_filename)[1]
    print('{}:{}: {}: {}'.format(fname, exc_tb.tb_lineno,exc_type.__name__,exc_obj))

这导致

annoying.py:5: UserWarning: I know!  How about if we are just maximally annoying?!