{"id":7610,"date":"2021-01-20T12:15:28","date_gmt":"2021-01-20T06:45:28","guid":{"rendered":"http:\/\/www.pythonpool.com\/?p=7610"},"modified":"2026-07-13T12:31:06","modified_gmt":"2026-07-13T07:01:06","slug":"plus-equal-to-in-python","status":"publish","type":"post","link":"https:\/\/www.pythonpool.com\/plus-equal-to-in-python\/","title":{"rendered":"Python += Operator: Add and Assign With Examples"},"content":{"rendered":"

Quick answer:<\/strong> The += operator combines the current value with a right-hand value and assigns the result back to the variable. It may perform an in-place update for mutable objects or create a new object for immutable ones, so value equality does not tell the whole story.<\/p>\n

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+= combines an existing value with a right-hand value and assigns the result, but mutable and immutable types can update differently.<\/figcaption><\/figure>\n

The Python +=<\/code> operator is augmented assignment. It adds the right-hand value to the left-hand target, then stores the result back into that target.<\/p>\n

The official Python documentation covers augmented assignment statements<\/a>, __iadd__()<\/a>, and mutable sequence types<\/a>.<\/p>\n

For numbers, x += y<\/code> is usually equivalent to x = x + y<\/code>. For mutable objects such as lists, +=<\/code> may update the object in place instead of creating a separate object.<\/p>\n

That difference matters when another name points to the same list. In-place updates are visible through both names, while rebinding with +<\/code> can leave the older list unchanged.<\/p>\n

Use +=<\/code> when it makes the update clearer and when in-place behavior is acceptable for the type involved.<\/p>\n

A useful way to read the operator is “add this and keep the result here.” The exact mechanics depend on the left-hand object. Some objects support an in-place update, while others return a new object and then store that result under the target name.<\/p>\n

When debugging, compare behavior with a second name pointing at the same object. If the second name sees the change, the object was updated in place. If it does not, the target was rebound to a separate object.<\/p>\n

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