不知道这个卡塔

Question

I'm working on this Kata in CodeWars, and I pass all but one test, but it doesn't say what the error is. The description says to check both lists for multiplicities. List a2 is a list of squares of list a1. I need to check a1 for the square root of all the items in a2, and return false if the array is empty, None, or the square root isn't in a1.

I am hoping to get any tips you might have about not only function (make it more Pythonic), but error handling. What am I missing? Why is it not passing? Thanks in advance.

def comp(a1, a2):
    if a1 == [] or a2 == []:
        return False
    if a1 == None or a2 == None:
        return False
    pos_count = 0
    neg_count = 0
    for num in set(a2):
        if num**0.5 in set(a1):
            pos_count += 1
        else:
            neg_count += 1
    if neg_count > 0:
        return False
    else:
        return True

Answer 1

Your can improve the code you posted as a comment:

def comp(a1, a2):
    if a1 is None or a2 is None:
        return False
    num_squared = []
    for num1 in a1:
        num_squared.append(num1**2)
    if set(a2) == set(num_squared):
        return True
    else:
        return False

You can build sequences using a comprehension expression. You build a list by appending squares to an empty list, but you could do it like so:

num_squared = [num ** 2 for num in a1]

You create a temporary set object set(num_squared) . However, you could build a set in the same way as the list instead:

num_squared = {num ** 2 for num in a1}

If you have a boolean expression and then return True else False you can replace it with the expression itself:

return set(a2) == set(num_squared)

Applying all these changes you can get:

def comp(a1, a2):
    if a1 is None or a2 is None:
        return False
    else:
        return set(a2) == {num ** 2 for num in a1}

edit: Just to note:

Empty lists evaluate as False in boolean expressions:

>>> bool([])
False

Also, None evaluates False :

>>> bool(None)
False