pay-attention

Q: What is output for list1,2,3 ?

def extendList(val, list=[]):
    list.append(val)
    return list

list1 = extendList(10)
list2 = extendList(123,[])
list3 = extendList('a')

print ("list1 = ", list1)
print ("list2 = ", list2)
print ("list3 = ", list3)

Wrong answer : list1 = [10], list2 = [123], list3 = [‘a’]

Correct answer :

How could we change to it ?

def extendList(val, list=None):
  if list is None:
    list = []
  list.append(val)
  return list