Functions

Write a function called double that returns twice its argument, then print double(5).

# define double, then print double(5)

return hands the value back; print only shows it.

def double(n):
    return n * 2

print(double(5))

This prints but returns nothing, so result is None. Fix it.

def double(n):
    print(n * 2)

result = double(5)
print(result + 1)

Return the value instead of printing it inside the function.

def double(n):
    return n * 2

result = double(5)
print(result + 1)

Pass the shout function into apply_twice so it is applied twice to hey.

def shout(word):
    return word.upper() + "!"

def apply_twice(fn, value):
    return fn(fn(value))

# call apply_twice with shout and "hey"

Pass the function without brackets; brackets would call it.

def shout(word):
    return word.upper() + "!"

def apply_twice(fn, value):
    return fn(fn(value))

print(apply_twice(shout, "hey"))