Does hashlib support a file mode?
steve+comp.lang.python at pearwood.info
Fri Jul 8 03:46:12 CEST 2011
Andrew Berg wrote:
> On 2011.07.07 08:39 AM, Phlip wrote:
>> On Jul 7, 6:24 am, Andrew Berg <bahamutzero8... at gmail.com> wrote:
>> > On 2011.07.07 08:11 AM, Phlip wrote:> No, I was pointing out that
>> > passing a type is more ... typesafe.
>> > None is a type.
>> I never said it wasn't.
Unfortunately, it isn't.
None is not a type, it is an instance.
>>> isinstance(None, type) # is None a type?
>>> isinstance(None, type(None)) # is None an instance of None's type?
So None is not itself a type, although it *has* a type:
>>> isinstance(type(None), type) # is NoneType itself a type?
> You are talking about this code, right?
> def file_to_hash(path, m=None):
> if m is None:
> m = hashlib.md5()
> What's not a type? The is operator compares types (m's value isn't the
> only thing compared here; even an separate instance of the exact same
> type would make it return False), and m can't be undefined.
The is operator does not compare types, it compares instances for identity.
There is no need for is to ever care about the type of the arguments --
that's just a waste of time, since a fast identity (memory location) test
This is why I initially thought that Phlip was joking when he suggested
that "m is None" could be type-unsafe. It doesn't matter what type m
has, "m is <anything>" will always be perfectly safe.
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