72 lines
1.9 KiB
Python
72 lines
1.9 KiB
Python
import contextlib
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import os
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import sys
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import random
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import string
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class ImportKiller:
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"Context manager to make an import of a given name or names fail."
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def __init__(self, *names):
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self.names = names
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def find_module(self, fullname, path=None):
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if fullname in self.names:
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return self
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def load_module(self, fullname):
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assert fullname in self.names
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raise ImportError(fullname)
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def __enter__(self):
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self.original = {}
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for name in self.names:
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self.original[name] = sys.modules.pop(name, None)
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sys.meta_path.insert(0, self)
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def __exit__(self, *args):
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sys.meta_path.remove(self)
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for key, value in self.original.items():
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if value is not None:
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sys.modules[key] = value
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@contextlib.contextmanager
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def NoNoneDictMutator(destination, **changes):
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"""Helper context manager to make and unmake changes to a dict.
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A None is not a valid value for the destination, and so means that the
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associated name should be removed."""
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original = {}
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for key, value in changes.items():
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original[key] = destination.get(key)
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if value is None:
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if key in destination:
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del destination[key]
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else:
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destination[key] = value
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yield
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for key, value in original.items():
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if value is None:
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if key in destination:
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del destination[key]
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else:
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destination[key] = value
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def Environ(**changes):
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"""A context manager to temporarily change the os.environ"""
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return NoNoneDictMutator(os.environ, **changes)
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ALPHABET = string.ascii_letters + string.digits
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def random_string(k, source=ALPHABET):
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"""Generate a random string with length <i>k</i>"""
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result = ''
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for i in range(0, k):
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result += random.choice(source)
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return result
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