python 2.7 - How exactly do the hashlib hashers treat input? -


the python 2.7 documentation has hashlib hashers: 

hash.update(arg)      update hash object string arg. [...]

but have seen people feed objects not strings, e.g. buffers, numpy ndarrays.

given python's duck typing, i'm not surprised possible specify non-string arguments.

the question is: how know hasher doing right thing argument?

i can't imagine hasher naïvely doing shallow iteration on argument because fail miserably ndarrays more 1 dimension - if shallow iteration, ndarray n-1 dimensions.

update unpacks arguments using s# format spec. means can either string, unicode or buffer interface.

you can't define a buffer interface in pure python, c libraries numpy can , - allows them passed hash.update.

things multiple dimension arrays work fine - on c level they're stored contiguous series of bytes.


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