why does my function is returning data type None??: Python datatype None

问题

This is my python code for printing an absolute number. My function is returning type None. I am not getting what I have done wrong. Please help me.

def n(num):
    if num<0:
        return (num*-1)

no = input("Enter a number: ")
print "Absolute Value is: "
print n(no)

回答1:

def n(num):
    if num<0:
        return (num*-1)
    else:
        return num


no = input("Enter a number: ")
print "Absolute Value is: "
print n(no)

writing an else statement will return num >= 0

Thank You :)

回答2:

The return is on the condition. Try :

def n(num):
    if num<0:
        num *= -1
    return num

no = int(input("Enter a number: "))
print "Absolute Value is: "
print n(no)

回答3:

You really don't need your own function for absolute value...

no = input("Enter a number: ")
print "Absolute Value is: ", abs(no)

来源：https://stackoverflow.com/questions/35228553/why-does-my-function-is-returning-data-type-none-python-datatype-none