Why does the Len(arr) return 7

Question

Won't the function call for f(range(5)) result into initialization of another arr with Len=0 and that led to arr of Len=3 and print sum of Len of array =5 .
Why does the arr have elements [0,2,0,2,4,0,2,0,2,4] when we return the arr.
What is the logic of the execution of the function?

https://code.sololearn.com/cR2GvEyC55O1/?ref=app

Answer 1

This is a gotcha when using mutable types as a value for a default parameter. In order to avoid this use None and then check inside the function if the parameter is equal to None. If so then you can set the local variable to an empty list.

def example(v, arr=None):
if arr is None:
arr = []
....
....

Answer 2

Thanks Bagon ,ChaoticDawg

Answer 3

Thanks Bagon

Answer 4

Bagon can you please help with some material on default arguments . I am trying to find it but am not able to find one . And also some material on python as well ?

Answer 5

Why does on returning the array it returns [0,2,0,2,4,0,2,0,2,4]