Python - passing arguments to a function

Question

Why, when you call f for the second time (f(range(5))), "arr" generated by first call (f(range(4))) is passed to f?

def f(values,arr=[]):
for i in values:
if i%2==0:
arr.append(i)
print(arr)
print(len(arr))
print("--------")
return len(arr)
print(f(range(4))+f(range(5)))

Answer 1

In the way your variable arr=[] is declared, it works as a persistent variable with a kind of memoization. This means, the variable will NOT be reset if the function call is repeated. The lifetime of the variable will only end if the program is terminated.
To get rid of this effect, move the initialization of arr from the function header to the first line of the function body.

Answer 2

All the calls used the 1 same list.

Answer 3

I'm a beginner so I can be wrong but I think the variables generated by a function are local/temporary variables so everytime you call that function again the values will reset (the list is same, just the values reset for every call) unless you declare the variable as a global variable.