Swapping values without using a temporary variable (Python recipe) by Hamish Lawson

ActiveState Code (http://code.activestate.com/recipes/65112/)

Runtime penalty. This is great for basic coding, but for inner loops use the temporary variable.

This comes straight from the Python Tutorial, section 10.10 on Performance Measurement.

>>> from timeit import Timer
>>> Timer('t=a; a=b; b=t', 'a=1; b=2').timeit()
0.60864915603680925
>>> Timer('a,b = b,a', 'a=1; b=2').timeit()
0.8625194857439773

http://www.python.org/doc/2.3.3/tut/node12.html

I found tuple method is faster. don't know the reason but this is what I got on my system

>>> from timeit import Timer



>>> Timer('t=a; a=b; b=t', 'a=1; b=2').timeit()

0.25679183006286621

>>> Timer('a,b = b,a', 'a=1; b=2').timeit()

0.20631599426269531

so bye to temp variables

a=5 b=6 print(a,b) a=a+b b=a-b a=a-b print(a,b)

a = a ^ b b = a ^ b a = a ^ b

Python now optimizes out the temporary tuple construction and unpacking. So go ahead and use the short form a,b = b,a. Not sure what the XOR method has going for it... less readable, less performant, and only works if the values are both the same type and __xor__ is defined for that type.