如何通过 warnings.warn 抑制源上下文的打印？

Question

如果我将以下代码片段放入文件 annoying.py:

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

...和运行它在 Unix shell 中，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)

（我得到与 Python 3.7.3 和 2.7.16 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，这种无端的混乱变得尤其成问题。）

如何抑制 second/clutter 行？

Answer 1

从 warnings.py 源代码看来 msg.line 控制是否需要打印该额外行。可以猴子修补 WarningMessage 的 init，使 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 选项使警告作为错误出现：

% python -Werror::UserWarning annoying.py

如果您有关注 annoying.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

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))

结果是

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

如何通过 warnings.warn 抑制源上下文的打印？

How to suppress the printing of source context by warnings.warn?

python

warnings