Why some builtin methods in python requires assigning to a variable? -


i confused python treats below examples.

example 1

   >>> = '{}'    >>> a.format('1')    '1'    >>>    '{}'    >>>

example 2

>>> = [] >>> a.append(1) >>> [1]

in example 1, 'a' '{}' in example 2, 'a' [1]

in both examples, i'm not assigning result 'a', what's difference?

answering on broader sense require more detail study particular case difference crops because 1 of object mutable , other non-mutable.

you cannot expect call method on string , change it. supposed create new string object.

for list.append, because mutable, method call can update list in place.


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