[Python-Dev] Subtle difference between f-strings and str.format() (original) (raw)

Serhiy Storchaka storchaka at gmail.com
Wed Mar 28 15:12:06 EDT 2018


28.03.18 22:05, Paul Moore пише

I can't imagine (non-contrived) code where the fact that a is formatted before b is evaluated would matter, so I'm fine with option 3.

If formatting a and evaluating b both raise exceptions, the resulting exception depends on the order.

$ ./python -bb
 >>> a = b'bytes'
 >>> '{}{}'.format(a, b)
Traceback (most recent call last):
   File "<stdin>", line 1, in <module>
NameError: name 'b' is not defined
 >>> f'{a}{b}'
Traceback (most recent call last):
   File "<stdin>", line 1, in <module>
BytesWarning: str() on a bytes instance

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