Menu
In Python, is there any difference (semantics, efficiency, etc.) between writing x = x+1 and x += 1?
961
Difference between x++ and x=x+1 in Java. In x++, it increase the value of x by 1 and in x=x+1 it also increase the value of x by 1. But the question is that both are same or there is any difference between them.
With x = x + 1 , the interpreter will treat it like x = x. __add__(1) , while x += 1 will be x = x. __iadd(1) , which can be much more efficient because it doesn't necessarily need to make a copy of x . x += 1 actually becomes x = x.
i+=1 does the same as i=i+1 there both incrementing the current value of i by 1. Do you mean "i += 1"? If so, then there's no difference.
The difference is that one modifies the data-structure itself (in-place operation) b += 1 while the other just reassigns the variable a = a + 1 .
Yes. Depending on how the class of x is coded, the short form has the option to modify x in-place, instead of creating a new object representing the sum and rebinding it back to the same name. This has an implication if you have multiple variables all referring to the same object - eg, with lists:
>>> a = b = []
>>> a += [5]
>>> a
[5]
>>> b
[5]
>>> a = a + [5]
>>> a
[5, 5]
>>> b
[5]
This happens because behind the scenes, the operators call different magic methods: + calls __add__ or __radd__ (which are expected not to modify either of their arguments) and += tries __iadd__ (which is allowed to modify self if it feels like it) before falling back to the + logic if __iadd__ isn't there.
185
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
