Is there a standardized method to swap two variables in Python?

Question

In Python, I've seen two variable values swapped using this syntax:

left, right = right, left

Is this considered the standard way to swap two variable values or is there some other means by which two variables are by convention most usually swapped?

Answer 1

Python evaluates expressions from left to right. Notice that while evaluating an assignment, the right-hand side is evaluated before the left-hand side.

http://docs.python.org/3/reference/expressions.html#evaluation-order

That means the following for the expression a,b = b,a :

• the right-hand side b,a is evaluated, that is to say a tuple of two elements is created in the memory. The two element are the objects designated by the identifiers b and a, that were existing before the instruction is encoutered during an execution of program
• just after the creation of this tuple, no assignement of this tuple object have still been made, but it doesn't matter, Python internally knows where it is
• then, the left-hand side is evaluated, that is to say the tuple is assigned to the left-hand side
• as the left-hand side is composed of two identifiers, the tuple is unpacked in order that the first identifier a be assigned to the first element of the tuple (which is the object that was formely b before the swap because it had name b)
  and the second identifier b is assigned to the second element of the tuple (which is the object that was formerly a before the swap because its identifiers was a)

This mechanism has effectively swapped the objects assigned to the identifiers a and b

So, to answer your question: YES, it's the standard way to swap two identifiers on two objects.
By the way, the objects are not variables, they are objects.