# numpy.testing.assert_warns

testing.assert_warns(warning_class, *args, **kwargs)

  Fail unless the given callable throws the specified warning.

  A warning of class warning_class should be thrown by the callable when invoked with arguments args and keyword arguments kwargs. If a different type of warning is thrown, it will not be caught.

  If called with all arguments other than the warning class omitted, may be used as a context manager:

  > with assert_warns(SomeWarning):

  >   do_something()

  The ability to be used as a context manager is new in NumPy v1.11.0.

  New in version 1.4.0.

  Parameters
    warning_class class

      The class defining the warning that func is expected to throw.

    func callable, optional

      Callable to test

    *args Arguments

      Arguments for func.

    **kwargs Kwargs

      Keyword arguments for func.

  Returns
    The value returned by func.

  Examples

      >>> import warnings
      >>> def deprecated_func(num):
      ...     warnings.warn("Please upgrade", DeprecationWarning)
      ...     return num*num
      >>> with np.testing.assert_warns(DeprecationWarning):
      ...     assert deprecated_func(4) == 16
      >>> # or passing a func
      >>> ret = np.testing.assert_warns(DeprecationWarning, deprecated_func, 4)
      >>> assert ret == 16

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