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patched = {}
def patch(namespace, name, value):
""" rebind the 'name' on the 'namespace' to the 'value',
possibly and remember the original value. Multiple
invocations to the same namespace/name pair will
remember a list of old values.
"""
nref = (namespace, name)
orig = getattr(namespace, name)
patched.setdefault(nref, []).append(orig)
setattr(namespace, name, value)
return orig
def revert(namespace, name):
""" revert to the orginal value the last patch modified.
Raise ValueError if no such original value exists.
"""
nref = (namespace, name)
if nref not in patched or not patched[nref]:
raise ValueError, "No original value stored for %s.%s" % nref
current = getattr(namespace, name)
orig = patched[nref].pop()
setattr(namespace, name, orig)
return current
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