Print function result but two line with a None is printed

Question

Create a function named same_name() that has two parameters named
your_name and my_name.

If our names are identical, return True. Otherwise, return False.

My code:

def same_name(your_name, my_name):
  if your_name == my_name:
    print(True)
  else:
    print(False)
  
print(same_name("Colby", "Colby"))
print(same_name("Tina", "Amber"))

The output is:

print(same_name("Colby", "Colby"))
# True
# None
print(same_name("Tina", "Amber"))
# False
# None

But the expected output is:

print(same_name("Colby", "Colby"))
# True
print(same_name("Tina", "Amber"))
# False

Where None is coming from?

Asked By: Mahmud Rahimli

||

Source

Answer 1

return, not print

It’s a common mistake to print instead of return. If a function need to return a value, print won’t do it, it’s just for the user, commonly used to debug. Since there is no return statement in your function, the function return None by default. In print(same_name("Colby", "Colby")), you print the returned value of the function, which is None, so you print a second time (the first one is in the function) with a None value.

  if your_name == my_name:
    return True
  else:
    return False

Usually, there is two types of exercises, those who ask you to create/code a function, and those who doesn’t.

When you don’t need a function:

Example with your exercise:

Ask two names to the user. If the first name is equal to the second
name, print True, if not, print False.

The expected code would be something like this:

name_1 = input('name?')
name_2 = input('name?')
if name_1 == name_2:
    print(True)
else:
    print(False)

or the shorter alternative:

name_1 = input('name?')
name_2 = input('name?')
print(name_1 == name_2)

When you do need a function:

Example with your exercise:

Create a function called same_name that takes two names. If the first name are equal
to the second name, return True, if not, return False.

The expected code would be something like this:

def same_name(name_1, name_2):
    if name_1 == name_2:
        return True
    else:
        return False

or the shorter alternative:

def same_name(name_1, name_2):
    return name_1 == name_2

If you run the program with the function, you won’t print anything, even if you call the function like same_name("Colby", "Colby"). It’s because return doesn’t print anything, it quit the function with a value. That’s why they surrounded the function call with print, to print the returned value, see the result and make sure it match the expected behavior.

Notes: The recommended practice is to return the condition result

The recommended practice is to return the condition result instead of branching with if:

def same_name(your_name, my_name):
    return your_name == my_name

Answered By: Dorian Turba

Print function result but two line with a None is printed

Question:

Answers:

return, not print

When you don’t need a function:

When you do need a function:

Notes: The recommended practice is to return the condition result