Question

this is my code :

a=[1,0,None,3]

def b(my_list):
    for i in range(len(my_list)):
        if not my_list[i]:
            a.remove(my_list[i])
        else:
            do_something()
    return my_list

a = b(a)
print a

and the error is :

Traceback (most recent call last):
  File "c.py", line 18, in <module>
    a = b(a)
  File "c.py", line 12, in b
    if not my_list[i]:
IndexError: list index out of range

so what can i do ,

thanks

Answer 1

You are modifying the same list that you’re iterating over, inside your loop. You can fix this by making a copy of the list and returning that:

def b(my_list):
    new_list = my_list[:]
    for i in range(len(my_list)):
        if not my_list[i]:
            new_list.remove(my_list[i])
        else:
            do_something()
    return new_list

Normally in Python, when you call a function such as b(a), then inside b, the parameter my_list is a reference to the same list as was passed in (a). The statement new_list = my_list[:] makes a copy of the list that you can modify and return inside the function.