[Python:OutputExplanation] Someone explain me output of this code. def func(a, L=[]): L.append(a) return(L)

Question

I am confused with the output of this code
def f(a,L=[]):
L.append(a)
return(L)

print(f(3), f(4))

I am confused how is appended value to List L is memorized even after function exits?

https://code.sololearn.com/czlOon5UjyaJ/#py

Answer 1

I asked a similar question a while back

https://www.sololearn.com/Discuss/1017883/?ref=app

The best answer was from John Wells

https://docs.quantifiedcode.com/JUMP_LINK__&&__python__&&__JUMP_LINK-anti-patterns/correctness/mutable_default_value_as_argument.html

Answer 2

i confuse too with your question.

first that create a function with a and L (list) default argument

than, a is inserted to L and finally return the L list.