This repository was archived by the owner on Dec 10, 2018. It is now read-only.
This repository was archived by the owner on Dec 10, 2018. It is now read-only.
Default values for TPayload objects change if instance is modified. #261
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Description
If you:
- have TPayload object with a default value
- make an instance with the default values
- mutate that instance
all subsequent default instances have new defaults. The snippet below will reproduce
from thriftpy import thrift
class Person(thrift.TPayload):
thrift_spec = {
1: (thrift.TType.LIST, "phones", thrift.TType.I32),
}
default_spec = [("phones", [])]
p = Person()
p.phones.append(3)
p2 = Person()
assert p2.phones == [] # FAIL. default is now [3]
In Python, default values for function/methods are re-used across uses. http://docs.python-guide.org/en/latest/writing/gotchas/#mutable-default-arguments
We can solve this by requiring that default values actually be callables eg
default_spec = [("phones", list)]
or systematically making copies of the default values eg
class AltPerson(object):
default_spec = [
('phones', []),
]
def __init__(self, **kwargs):
for name, default_value in self.default_spec:
if name in kwargs:
value = kwargs[name]
else:
value = copy.copy(default_value)
setattr(self, name, value)
If you go with the first option (my preference), it becomes tricky to intentionally create TPayload objects with callable attributes. Eg if you wanted phones to be set to an object that is both indexable f[0] and callable f(). That said, if you're in that camp, you ought to know what you're doing and can do `Person(phones=
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