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63 lines
2.8 KiB
63 lines
2.8 KiB
11 years ago
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supported_operations = ["__add__", "__sub__", "__mul__", "__floordiv__", "__mod__", "__divmod__", "__pow__", "__lshift__", "__rshift__", "__and__", "__xor__", "__or__", "__pow__", "__div__", "__truediv__", "__div__", "__radd__", "__rsub__", "__rmul__", "__rdiv__", "__rtruediv__", "__rfloordiv__", "__rmod__", "__rdivmod__", "__rpow__", "__rlshift__", "__rrshift__", "__rand__", "__rxor__", "__ror__", "__sub__", "__rpow__", "__radd__", "__neg__", "__pos__", "__abs__", "__complex__", "__long__", "__float__", "__oct__", "__hex__", "__index__", "__len__"]
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class Wrapper(object):
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"""Wrap a value so that it will be lazy-evaluated. `wrapper.value` returns the current value (you can also use c(wrapper))."""
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def __init__(self, target, attribute=None, arguments=None):
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self.target = target
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self.attribute = attribute
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self.arguments = arguments
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if attribute is not None and arguments is not None:
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raise TypeError
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@property
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def value(self):
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if self.attribute is None and self.arguments is None:
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return self.target
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if self.attribute is not None:
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return getattr(c(self.target), self.attribute)
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if self.arguments is not None:
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return c(self.target)(*map(c, self.arguments))
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@value.setter
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def value(self, new_target):
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self.target = new_target
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def __getattr__(self, name):
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return Wrapper(self, attribute=name)
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def __call__(self, *args):
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return Wrapper(self, arguments=args)
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def __repr__(self): return str(self)
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def __str__(self):
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if self.attribute is None and self.arguments is None:
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return "w(" + str(self.target) + ")"
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if self.attribute is not None:
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return "w(" + str(self.target) + "." + str(self.attribute) + ")"
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if self.arguments is not None:
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return "w(" + str(self.target) + "(" + ",".join(map(str, self.arguments)) + ")"
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def pass_through(operation):
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return lambda self, *others: Wrapper(Wrapper(self, attribute=operation), arguments=others)
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for operation in supported_operations:
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setattr(Wrapper, operation, pass_through(operation))
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def c(g):
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"""Get the current value of a wrapper or bare variable."""
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if isinstance(g, Wrapper): return g.value
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else: return g
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def wrap(v):
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"""Wrap a variable, or just return it if it's already wrapped."""
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if isinstance(v, Wrapper): return v
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else: return Wrapper(v)
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if __name__ == "__main__":
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foo, bar, baz = wrap(1), wrap(2), wrap(3)
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print("foo, bar, and baz are the wrapped values 1, 2, and 3.")
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boop = foo + bar*baz
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print("boop is set to foo + bar*baz: %s" % (boop, ))
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print("And we can fetch the value of that computation easily as boop.value: %s" % (boop.value, ))
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print
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print("We can change the value of foo:")
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print(">>> foo.value = 5")
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foo.value = 5
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print("And now, when we fetch the value of boop, it is adjusted accordingly:")
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print(">>> boop.value => %s" % (boop.value,))
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print
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print("There is also a shorthand for evaluating a glomp: c(boop) => %s" % (c(boop), ))
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