В Python операторы += и + являются разными. За их поведение отвечают методы __iadd__ и __add__ соответственно.class A: def __init__(self

Библиотека Python разработчика | Книги по питону

В Python операторы += и + являются разными. За их поведение отвечают методы __iadd__ и __add__ соответственно.


class A:
    def __init__(self, x):
        self.x = x

    def __iadd__(self, another):
        self.x += another.x
        return self

    def __add__(self, another):
        return type(self)(self.x + another.x)

Если __iadd__ не определён, выражение a += b сводится к простому a = a + b.

Обычно разница между += и + в том, что первый изменяет объект, а второй создаёт новый:


>>> a = [1, 2, 3]
>>> b = a
>>> a += [4]
>>> a
[1, 2, 3, 4]
>>> b
[1, 2, 3, 4]
>>> a = a + [5]
>>> a
[1, 2, 3, 4, 5]
>>> b
[1, 2, 3, 4]

👉@BookPython

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Create: 2025-06-05
Last Update: 2025-06-15 00:40:12

В Python операторы += и + являются разными. За их поведение отвечают методы __iadd__ и __add__ соответственно.


class A:
    def __init__(self, x):
        self.x = x

    def __iadd__(self, another):
        self.x += another.x
        return self

    def __add__(self, another):
        return type(self)(self.x + another.x)


>>> a = [1, 2, 3]
>>> b = a
>>> a += [4]
>>> a
[1, 2, 3, 4]
>>> b
[1, 2, 3, 4]
>>> a = a + [5]
>>> a
[1, 2, 3, 4, 5]
>>> b
[1, 2, 3, 4]

👉@BookPython

BY Библиотека Python разработчика | Книги по питону

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