why does the function memorize the last return result when I call the same function again?

Question

the sample code(python3):

def fuc(x,l=[]):
l.append(x)
print(l)
fuc(1)
fuc(1)
fuc(1)

the result will be:
[1]
[1,1]
[1,1,1]

instead of :
[1]
[1]
[1]

so why can the func memerize?

and what can do to get rid of the memory after the last call?

Answer 1

https://www.sololearn.com/Discuss/1748873/?ref=app

Answer 2

Here you'll find the answer:
https://code.sololearn.com/cmmVaC1aWcc5/?ref=app