Is There a Standardized Method to Swap Two Variables in Python

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

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

Python docs: 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 elements are the objects designated by the identifiers b and a, that were existing before the instruction is encountered during the execution of the program.
• Just after the creation of this tuple, no assignment of this tuple object has 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 formerly 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.

How swapping variables is implemented in Python?

It's a simple bytecode operation which doesn't need any intermediate variables to do the swap. See this demo:

import dis

code = '''
a = input()
b = input()
a, b = b, a
'''

dis.dis(code)

Output:

 2           0 LOAD_NAME                0 (input)
             2 CALL_FUNCTION            0
             4 STORE_NAME               1 (a)

 3           6 LOAD_NAME                0 (input)
             8 CALL_FUNCTION            0
            10 STORE_NAME               2 (b)

 4          12 LOAD_NAME                2 (b)
            14 LOAD_NAME                1 (a)
            16 ROT_TWO
            18 STORE_NAME               1 (a)
            20 STORE_NAME               2 (b)
            22 LOAD_CONST               0 (None)
            24 RETURN_VALUE

Note: Like bytecode as a whole, this is of course just an implementation detail of CPython.

How do you swap two local variables within a function in python

I think this is what you want to achieve:

def twobytwo(m):
    last = len(m)-1
    for i in range(0, last):
        m[i][i], m[i][last] = m[i][last], m[i][i]
        m[i][i], m[last][last] = m[last][last], m[i][i]
        m[i][i], m[last][i] = m[last][i], m[i][i]
    return m

print(twobytwo([[0, 1], [2, 3]]))

EDIT:
If you still want to maintain the function swap:

def swap(i, j):
    return j, i

a, b = swap(a, b)

But I think a, b = b, a is good enough.

Python: how to change values of two dictionaries

Try this

worker_1, worker_2 = worker_2, worker_1

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