for testing and deploying your application
for finding and fixing issues
for empowering human code reviews
"""
Construction of sentinel objects.
Sentinel objects are used when you only care to check for object identity.
import sys
def sentinel(name, doc=None):
try:
value = sentinel._cache[name] # memoized
except KeyError:
pass
else:
if doc == value.__doc__:
return value
raise ValueError(
'attempted to create sentinel with a used name and a different'
' docstring: %r\noriginal docstring:\n%s' % (name, value.__doc__),
)
@object.__new__ # bind a single instance to the name 'Sentinel'
class Sentinel(object):
__doc__ = doc
__slots__ = ('__weakref__',)
__name__ = name
def __new__(cls):
raise TypeError("Can't construct new instances of %r" % name)
def __repr__(self):
return 'sentinel(%r)' % name
def __reduce__(self):
return sentinel, (name, doc)
def __deepcopy__(self, _memo):
return self
def __copy__(self):
cls = type(Sentinel)
# traverse up one frame to find the module where this is defined
cls.__module__ = sys._getframe(1).f_globals['__name__']
except (AttributeError, ValueError, KeyError):
# Couldn't get the name from the calling scope, just use None.
cls.__module__ = None
sentinel._cache[name] = Sentinel # cache result
return Sentinel
sentinel._cache = {}
quantopian /
zipline
