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https://github.com/wassname/catalyst.git
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llllllllll
88a53fbdd1
Moves _nop_context to context_tricks under the name nop_context. Uses an explicit object for the actual context manager in callback manager.
74 lines
1.9 KiB
Python
74 lines
1.9 KiB
Python
@object.__new__
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class nop_context(object):
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"""A nop context manager.
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"""
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def __enter__(self):
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pass
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def __exit__(self, *excinfo):
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pass
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def _nop(*args, **kwargs):
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pass
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class CallbackManager(object):
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"""Create a context manager from a pre-execution callback and a
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post-execution callback.
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Parameters
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----------
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pre : (...) -> any, optional
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A pre-execution callback. This will be passed ``*args`` and
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``**kwargs``.
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post : (...) -> any, optional
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A post-execution callback. This will be passed ``*args`` and
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``**kwargs``.
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Notes
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-----
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The enter value of this context manager will be the result of calling
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``pre(*args, **kwargs)``
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Examples
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--------
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>>> def pre(where):
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... print('entering %s block' % where)
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>>> def post(where):
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... print('exiting %s block' % where)
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>>> manager = CallbackManager(pre, post)
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>>> with manager('example'):
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... print('inside example block')
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entering example block
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inside example
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exiting example block
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These are reusable with different args:
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>>> with manager('another'):
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... print('inside another block')
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entering another block
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inside another block
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exiting another block
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"""
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def __init__(self, pre=None, post=None):
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self.pre = pre if pre is not None else _nop
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self.post = post if post is not None else _nop
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def __call__(self, *args, **kwargs):
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return _ManagedCallbackContext(self.pre, self.post, args, kwargs)
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class _ManagedCallbackContext(object):
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def __init__(self, pre, post, args, kwargs):
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self._pre = pre
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self._post = post
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self._args = args
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self._kwargs = kwargs
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def __enter__(self):
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return self._pre(*self._args, **self._kwargs)
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def __exit__(self, *excinfo):
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self._post(*self._args, **self._kwargs)
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