What does a, b=b, a%b mean in a definition?

Question

Found it here

Also, does it read right to left or vice versa?

Please include any code relevant to your question in the question itself, not via links. But to answer the question, it's just a shorthand way to assign to both the `a` and `b` variables at once. It's like `a = b` then `b = a%b` but where the second assignment is using the *original* value of `a` rather than the new one. For example `a, b = b, a` lets you swap two variables over without requiring a temporary variable. — Robin Zigmond, Mar 06 '19 at 08:32
Possible duplicate of [How does Python's comma operator works during assignment?](https://stackoverflow.com/questions/11502268/how-does-pythons-comma-operator-works-during-assignment) — Robin Zigmond, Mar 06 '19 at 08:33
Possible duplicate of [Is there a standardized method to swap two variables in Python?](https://stackoverflow.com/questions/14836228/is-there-a-standardized-method-to-swap-two-variables-in-python) — Sanjeev S, Mar 06 '19 at 08:33
Possible duplicate of [Multiple assignment and evaluation order in Python](https://stackoverflow.com/questions/8725673/multiple-assignment-and-evaluation-order-in-python) — Thierry Lathuille, Mar 06 '19 at 08:40

score 1 · Answer 1 · answered Mar 06 '19 at 08:34

In assignment statements in python, the right-hand side is evaluated first before doing the actual setting of variables. So,

a , b = b, a%b

evaluates b (let's call the result temp1), evaluates a%b which is a mod b (call that temp2), then sets a to temp1 and b to temp2.

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