Increment/decrement operators in python?

Question

I'm a relative newbie to python, and this NG, but it's certainly growing on me.

One thing I'm missing is the increment/decrement operator from C, ie x++, and its ilk. Likewise x += y.

Is there any way of doing this in Python?

Answer 1

When you want to increment or decrements, you typically want to do that on an integer. Like so:

b++

But in Python, integers are immutable. That is you can't change them. This is because the integer objects can be used under several names. Try this:

>>> b = 5
>>> a = 5
>>> id(a)
162334512
>>> id(b)
162334512
>>> a is b
True

a and b above are actually the same object. If you incremented a, you would also increment b. That's not what you want. So you have to reassign. Like this:

b = b + 1

Or simpler:

b += 1

Which will reassign b to b+1. That is not an increment operator, because it does not increment b, it reassigns it.

Python behaves differently here, because it is not C, and is not a low level wrapper around machine code, but a high-level dynamic language, where increments don't make sense, and also are not as necessary as in C, where you use them every time you have a loop, for example.

Comments

Nice and proper explanation :)

Answer 2

Quick answer:
x += y works. (Well, it should.)
x++ doesn't.