[New-bugs-announce] [issue11494] Confusing error message from warnings.warn

Gerrit Holl report at bugs.python.org
Mon Mar 14 11:47:52 CET 2011

New submission from Gerrit Holl <topjaklont at gmail.com>:

When accidentally passing a string to warnings.warn where one should pass a Warning-class, the error message is rather confusing:

 $ ./python 
 Python 2.7.1+ (release27-maint:88766, Mar  8 2011, 16:51:59) 
 [GCC 4.4.5] on linux2
 Type "help", "copyright", "credits" or "license" for more information.
 >>> import warnings
 >>> warnings.warn("aaa", "bbb")
 Traceback (most recent call last):
   File "<stdin>", line 1, in <module>
 TypeError: issubclass() arg 1 must be a class

It would be better for the error message to say TypeError: warnings must be classes inherited from ... or something like that.

components: Interpreter Core, Library (Lib)
messages: 130800
nosy: Gerrit.Holl
priority: normal
severity: normal
status: open
title: Confusing error message from warnings.warn
type: behavior
versions: Python 2.7

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