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pythonprintingreturn

Printing out function containing print and return

I recently came across a weird problem. I assumed that the two code snippets below should have the same output, yet they do not. Can someone explain?

def my_function():
    myvar = "a"
    print("2", myvar)
    return myvar

print("1")
print(my_function())

#will output:
#1
#2 a
#a

print("1", my_function())

#will output:
#2 a
#1 a

I assumed that in the second example the "1" should be printed before the function is invoked and their internal print statement is run.

Solution

  • When you call a function with parameters, the parameters have to be fully evaluated before calling the function.

    In the case of 2. python effectively rewrites your code like this:

    _ = my_function()
print("1", _)

    So my_function() is called first, then the parameters are passed to print()