如何通过warnings.warn抑制源上下文的打印？

Question

If I put the following snippet in a file annoying.py :

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

...and run it in a Unix shell, this is what I get:

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

(I get the same output with Python 3.7.3 and 2.7.16.)

I want only the first line of this output to be printed.

With respect to what I'm working on, the second line only adds visually distracting clutter. (This gratuitous clutter becomes particularly problematic when there are a lot of warnings.)

How can I suppress the second/clutter line?

Answer 1

From warnings.py source code it seems that msg.line controls if that extra line needs to printed or not. One could monkey patch the WarningMessage's init such that self.line is "" instead of None as show below

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)

This results in:

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

Another hacky way to do maybe is to make the warnings come as errors by using -W option:

% python -Werror::UserWarning annoying.py

if you have following 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) 

results in

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

To get the filename, linenumber, type of warning and warning message, I had to do the following

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))

which results in

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