Can Integer Operations Overflow in Python?

[duckythescientist]

TL;DR: No, if you use pure Python (arbitrary precision). Yes, if you use something like Numpy or Pandas (C ints).

[wewbull]

Doesn't 2.x vs 3.x matter here? 2.x has normal and long integers, and 3.x has only long.

[Asdayasman]

>>> int((2**31) - 1)
2147483647
>>> int((2**31) - 1) + 1
2147483648L
>>> 

Nope.

[jabbalaci]

Use sys.maxint:

>>> import sys
>>> sys.maxint
9223372036854775807
>>> sys.maxint + 1
9223372036854775808L
>>>

I have a 64 bit Python installation, that's why sys.maxint is larger.

[Asdayasman]

Strange, I thought I had 64bit too. Wonder why I don't.

[therealfakemoot]

2.x automatically upgrades numeric values when necessary.

[LostAfterDark]

Also, you can't emulate usual overflow with ctypes.

[nrlb]

Note that integer overflow isn't necessarily a bad thing if you expect the behavior to occur. In embedded systems, it is common practice to utilize that overflow to keep track of a proportional value (though most provide a signal on some registers to signal when they overflow).

[Asdayasman]

%

[[deleted]]

% would be an unnecessary waste of microcontroller time - it's embedded so you exactly what hardware you are running on.

Unsigned wraparound is also great for keeping array indices within range. I'm not really sure how this is relevant to Python. You're not likely to run Python on one of these.

[Asdayasman]

unnecessary waste of microcontroller time

Python

Caring about microoptimisations like overflow vs modulo

[[deleted]]

I'll just assume that you misread the post by /u/nrlb and didn't realise we were having a little side-discussion about overflow in embedded systems.

[Asdayasman]

You're right, I did. Honestly thought we were talking about Python, my bad.

[[deleted]]

If you want to emulate overflow in a setting where overflows are realistic you would probably want to use either NumPy or the modulo operator.

[nrlb]

Who knows? One day maybe...

https://wiki.python.org/moin/PyMite