Python3 compatibility

[LangInteger]

In file CS61A/lab02/lab02_extra.py / , code

def cycle(f1, f2, f3):
    """Returns a function that is itself a higher-order function.
    >>> def add1(x):
    ...     return x + 1
    >>> def times2(x):
    ...     return x * 2
    >>> def add3(x):
    ...     return x + 3
    >>> my_cycle = cycle(add1, times2, add3)
    >>> identity = my_cycle(0)
    >>> identity(5)
    5
    >>> add_one_then_double = my_cycle(2)
    >>> add_one_then_double(1)
    4
    >>> do_all_functions = my_cycle(3)
    >>> do_all_functions(2)
    9
    >>> do_more_than_a_cycle = my_cycle(4)
    >>> do_more_than_a_cycle(2)
    10
    >>> do_two_cycles = my_cycle(6)
    >>> do_two_cycles(1)
    19
    """
    "*** YOUR CODE HERE ***"
    def func(n):
        def fun(x):
            te = x
            m = 1
            while m <= n:
                if m % 3 == 1:
                    te = f1(te)
                elif m % 3 == 2:
                    te = f2(te)
                else:
                    te = f3(te)
                m += 1
            return te
        return fun
    return func

This will lead to a error in python3 (at least in python 3.8 it does so), nonlocal n should be added to first line of fun.

Reference: Python nonlocal statement