Functions are first class objects

By functions being first-class objects, we mean that we can:

• assign functions to variables
• store functions in data structures
• pass functions as arguments to other functions
• return functions as values from other functions.

Assignment

def yell(text):
    return text.upper() + '!'

bark = yell
bark('woof')

Functions can be stored in data structures

funcs = [str.lower, str.capitalize]

for f in funcs:
    print(f('hey there'))

Functions can be passed to other functions

def yell(text):
    return text.upper() + '!'

map(yell, ['hello', 'hey', 'hi'])

Functions can be returned from other functions

def talk(volume):
    def whisper(text):
        return text.lower() + '...'
    def yell(text):
        return text.upper() + '!'

    if volume > 0.5:
        return yell
    else:
        return whisper

talk(0.8)("hello")