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92 lines
2.9 KiB
92 lines
2.9 KiB
"""
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Module defining global singleton classes.
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This module raises a RuntimeError if an attempt to reload it is made. In that
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way the identities of the classes defined here are fixed and will remain so
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even if numpy itself is reloaded. In particular, a function like the following
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will still work correctly after numpy is reloaded::
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def foo(arg=np._NoValue):
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if arg is np._NoValue:
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...
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That was not the case when the singleton classes were defined in the numpy
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``__init__.py`` file. See gh-7844 for a discussion of the reload problem that
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motivated this module.
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"""
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__ALL__ = [
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'ModuleDeprecationWarning', 'VisibleDeprecationWarning', '_NoValue'
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]
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# Disallow reloading this module so as to preserve the identities of the
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# classes defined here.
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if '_is_loaded' in globals():
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raise RuntimeError('Reloading numpy._globals is not allowed')
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_is_loaded = True
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class ModuleDeprecationWarning(DeprecationWarning):
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"""Module deprecation warning.
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The nose tester turns ordinary Deprecation warnings into test failures.
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That makes it hard to deprecate whole modules, because they get
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imported by default. So this is a special Deprecation warning that the
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nose tester will let pass without making tests fail.
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"""
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ModuleDeprecationWarning.__module__ = 'numpy'
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class VisibleDeprecationWarning(UserWarning):
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"""Visible deprecation warning.
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By default, python will not show deprecation warnings, so this class
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can be used when a very visible warning is helpful, for example because
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the usage is most likely a user bug.
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"""
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VisibleDeprecationWarning.__module__ = 'numpy'
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class _NoValueType:
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"""Special keyword value.
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The instance of this class may be used as the default value assigned to a
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keyword if no other obvious default (e.g., `None`) is suitable,
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Common reasons for using this keyword are:
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- A new keyword is added to a function, and that function forwards its
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inputs to another function or method which can be defined outside of
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NumPy. For example, ``np.std(x)`` calls ``x.std``, so when a ``keepdims``
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keyword was added that could only be forwarded if the user explicitly
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specified ``keepdims``; downstream array libraries may not have added
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the same keyword, so adding ``x.std(..., keepdims=keepdims)``
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unconditionally could have broken previously working code.
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- A keyword is being deprecated, and a deprecation warning must only be
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emitted when the keyword is used.
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"""
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__instance = None
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def __new__(cls):
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# ensure that only one instance exists
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if not cls.__instance:
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cls.__instance = super().__new__(cls)
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return cls.__instance
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# needed for python 2 to preserve identity through a pickle
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def __reduce__(self):
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return (self.__class__, ())
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def __repr__(self):
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return "<no value>"
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_NoValue = _NoValueType()
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