[Python-ideas] PEP 572: Assignment Expressions (post #4)

[Michel Desmoulin]

Le 11/04/2018 à 23:34, George Leslie-Waksman a écrit :
> I really like this proposal in the context of `while` loops but I'm
> lukewarm in other contexts.
> 
> I specifically like what this would do for repeated calls.
> 
> ...
> 
> md5 = hashlib.md5()
> with open(filename, 'rb') as file_reader:
>     while chunk := file_reader.read(1024):
>         md5.update(chunk)
> 
> seems really nice. I'm not sure the other complexity is justified by
> this nicety and I'm really wary of anything that makes comprehensions
> more complicated; I already see enough comprehension abuse to the point
> of illegibility.
> 
> --George
> 
> 

I like the new syntax, but you can already do what you want with iter():


md5 = hashlib.md5()
with open('/etc/fstab', 'rb') as file_reader:
    for chunk in iter(lambda: file_reader.read(1024), b''):
        md5.update(chunk)

Anyway, both use case fall short IRL, because you would wrap read in
huge try/except to deal with the mess that is letting a user access the
filesystem.