mirror of
https://github.com/wassname/catalyst.git
synced 2026-06-29 03:02:36 +08:00
Joe Jevnik
46 lines
969 B
Python
46 lines
969 B
Python
"""
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Control flow utilities.
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"""
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from six import iteritems
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class nullctx(object):
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"""
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Null context manager. Useful for conditionally adding a contextmanager in
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a single line, e.g.:
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with SomeContextManager() if some_expr else nullctx():
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do_stuff()
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"""
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def __enter__(self):
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return self
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def __exit__(*args):
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return False
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def invert(d):
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"""
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Invert a dictionary into a dictionary of sets.
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>>> invert({'a': 1, 'b': 2, 'c': 1}) # doctest: +SKIP
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{1: {'a', 'c'}, 2: {'b'}}
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"""
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out = {}
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for k, v in iteritems(d):
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try:
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out[v].add(k)
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except KeyError:
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out[v] = {k}
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return out
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def invert_unique(d, check=True):
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"""
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Invert a dictionary with unique values into a dictionary with (k, v) pairs
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flipped.
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"""
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if check:
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assert len(set(d.values())) == len(d), "Values were not unique!"
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return {v: k for k, v in iteritems(d)}
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