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What is the difference between the following Python expressions:
# First: x,y = y,x+y # Second: x = y y = x+y First gives different results than Second.
e.g.,
First:
>>> x = 1 >>> y = 2 >>> x,y = y,x+y >>> x 2 >>> y 3 Second:
>>> x = 1 >>> y = 2 >>> x = y >>> y = x+y >>> x 2 >>> y 4 y is 3 in First and 4 in Second
659
Multiple assignment in Python: Assign multiple values or the same value to multiple variables. In Python, use the = operator to assign values to variables. You can assign values to multiple variables on one line.
Multiple assignment is slower than individual assignment. For example "x,y=a,b" is slower than "x=a; y=b". However, multiple assignment is faster for variable swaps. For example, "x,y=y,x" is faster than "t=x; x=y; y=t".
Multiple Assignment in PythonPython allows you to assign a single value to several variables simultaneously. For example − a = b = c = 1. Here, an integer object is created with the value 1, and all three variables are assigned to the same memory location.
In an assignment statement, the right-hand side is always evaluated fully before doing the actual setting of variables. So,
x, y = y, x + y evaluates y (let's call the result ham), evaluates x + y (call that spam), then sets x to ham and y to spam. I.e., it's like
ham = y spam = x + y x = ham y = spam By contrast,
x = y y = x + y sets x to y, then sets y to x (which == y) plus y, so it's equivalent to
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