Guard clause

A guard clause helps you removing one level of nesting and resulting in flatter code.

Example

Before:

PYTHON
def is_gmail(email):
    if isinstance(email, str):
        if email.endswith("@gmail.com"):
            return True
        else:
            return False
    else:
        return False

After:

PYTHON
def is_gmail(email):
    if not isinstance(email, str):
        return False
    if not email.endswith("@gmail.com"):
        return False
    return True

Overkill?

Sometimes it is a bit of an overkill to use guard clause.

PYTHON
def drink(age):
    if age < 18:
        return
    print("Drinking...")

May be harder to read than just:

PYTHON
def drink(age):
    if age >= 18:
        print("Drinking...")