functions.py

# functions are first-class objects: assigned, stored, passed as arg, returned as output
def p(name):
    print(name)

r = p # assign to variable
r('Foo')

del p
r('Foo') # uderlying link still working

f_list = [r, str.capitalize, int.real] # store in data structure


def sum_num(a, b):
    print(a + b)

def handler(f, x, y):
    # higher-order function: accepts other functions as args
    f(x, y)

handler(sum_num, 4, 5)


# nested functions
def outer(x, y):
    def inner(a, b):
        return (a + b)
    return inner(x, y)

outer(3, 6) # outer defines and calls inner

def external(x):
    y = 20

    def internal():
        print(x + y)
    internal()

external(5)


# closure
def add(x, y):
    # do_add is a closure as it can access the parent function params
    def do_add():
        print('Adding', x, y)
        return x + y
    return do_add


def generate_power(number):
    def nth_power(power):
        return number ** power
    return nth_power

raise_two = generate_power(2) # generate_power returns a function
raise_three = generate_power(3)

raise_two(2)

# required and optional arguments: *args and **kwargs
def foo(required, *args, **kwargs):
    print(required)
    if args:
        print(args)
    if kwargs:
        print(kwargs)

# any number of positional arguments
# *args packs the positional arguments into a TUPLE
foo('hello', 1, 2, 3)

def sum_many(*args):
    '''sum any number of numbers'''
    s = 0
    for i in args:
        s += i
    print('sum is', s)

print(sum_many.__doc__) # docs strings
print(sum_many.__name__)

sum_many(1, 2, 3)
sum_many(1, 2, 3, 4, 5, 7, 8, 9, 10)

l1 = [1, 2, 3, 4, 5]
sum_many(*l1) # unpacking

# any number of keyword argument
# **kwargs packs the keyword arguments into a DICTIONARY
foo('hello', key1='world', key2=999)

def profile(**kwargs):
    '''print profile with any number of attributes'''
    for key, value in kwargs.items():
        print(key, ':', value)

profile(firt_name='John', last_name='Doe', age=25, job='tester')

# args and kwargs
def cheeseshop(kind, *arguments, **keywords):
    print('-> Do you have any', kind, '?')
    print('-> Sorry, we are all out of', kind)
    for arg in arguments:
        print(arg)
    print('<->' * 10)
    for kw in keywords:
        print(kw, ':', keywords[kw])

cheeseshop('Limburger')

cheeseshop('Limburger',
           'It is very runny, sir.',
           'It is really very, VERY runny, sir.',
           shopkeeper='Michael Palin',
           client='John Cleese',
           sketch='Cheese Shop Sketch')