วันที่ 14 — Higher Order Functions

def sum_numbers(nums):  # normal function
    return sum(nums)    # a sad function abusing the built-in sum function :<

def higher_order_function(f, lst):  # function as a parameter
    summation = f(lst)
    return summation
result = higher_order_function(sum_numbers, [1, 2, 3, 4, 5])
print(result)       # 15

def square(x):          # a square function
    return x ** 2

def cube(x):            # a cube function
    return x ** 3

def absolute(x):        # an absolute value function
    if x >= 0:
        return x
    else:
        return -(x)

def higher_order_function(type): # a higher order function returning a function
    if type == 'square':
        return square
    elif type == 'cube':
        return cube
    elif type == 'absolute':
        return absolute

result = higher_order_function('square')
print(result(3))       # 9
result = higher_order_function('cube')
print(result(3))       # 27
result = higher_order_function('absolute')
print(result(-3))      # 3

def add_ten():
    ten = 10
    def add(num):
        return num + ten
    return add

closure_result = add_ten()
print(closure_result(5))  # 15
print(closure_result(10))  # 20

# Normal function
def greeting():
    return 'Welcome to Python'
def uppercase_decorator(function):
    def wrapper():
        func = function()
        make_uppercase = func.upper()
        return make_uppercase
    return wrapper
g = uppercase_decorator(greeting)
print(g())          # WELCOME TO PYTHON

## Let us implement the example above with a decorator

def uppercase_decorator(function):
    def wrapper():
        func = function()
        make_uppercase = func.upper()
        return make_uppercase
    return wrapper
@uppercase_decorator
def greeting():
    return 'Welcome to Python'
print(greeting())   # WELCOME TO PYTHON

# First Decorator
def uppercase_decorator(function):
    def wrapper():
        func = function()
        make_uppercase = func.upper()
        return make_uppercase
    return wrapper

# Second decorator
def split_string_decorator(function):
    def wrapper():
        func = function()
        splitted_string = func.split()
        return splitted_string
    return wrapper

#Decorators will be executed from bottom to top
@split_string_decorator
@uppercase_decorator     # order with decorators is important in this case - .upper() function does not work with lists
def greeting():
    return 'Welcome to Python'
print(greeting())   # ['WELCOME', 'TO', 'PYTHON']

def decorator_with_parameters(function):
    def wrapper_accepting_parameters(para1, para2, para3):
        function(para1, para2, para3)
        print("I live in {}".format(para3))
    return wrapper_accepting_parameters

@decorator_with_parameters
def print_full_name(first_name, last_name, country):
    print("I am {} {}. I love to teach.".format(
        first_name, last_name))

print_full_name("Asabeneh", "Yetayeh",'Finland')

    # syntax
    map(function, iterable)

numbers = [1, 2, 3, 4, 5] # iterable
def square(x):
    return x ** 2
numbers_squared = map(square, numbers)
print(list(numbers_squared))    # [1, 4, 9, 16, 25]
# Lets apply it with a lambda function
numbers_squared = map(lambda x : x ** 2, numbers)
print(list(numbers_squared))    # [1, 4, 9, 16, 25]

numbers_str = ['1', '2', '3', '4', '5']  # iterable
numbers_int = map(int, numbers_str)
print(list(numbers_int))    # [1, 2, 3, 4, 5]

names = ['Asabeneh', 'Lidiya', 'Ermias', 'Abraham']  # iterable

def change_to_upper(name):
    return name.upper()

names_upper_cased = map(change_to_upper, names)
print(list(names_upper_cased))    # ['ASABENEH', 'LIDIYA', 'ERMIAS', 'ABRAHAM']

# Let us apply it with a lambda function
names_upper_cased = map(lambda name: name.upper(), names)
print(list(names_upper_cased))    # ['ASABENEH', 'LIDIYA', 'ERMIAS', 'ABRAHAM']

    # syntax
    filter(function, iterable)

# Lets filter only even nubers
numbers = [1, 2, 3, 4, 5]  # iterable

def is_even(num):
    if num % 2 == 0:
        return True
    return False

even_numbers = filter(is_even, numbers)
print(list(even_numbers))       # [2, 4]

numbers = [1, 2, 3, 4, 5]  # iterable

def is_odd(num):
    if num % 2 != 0:
        return True
    return False

odd_numbers = filter(is_odd, numbers)
print(list(odd_numbers))       # [1, 3, 5]

# Filter long name
names = ['Asabeneh', 'Lidiya', 'Ermias', 'Abraham']  # iterable
def is_name_long(name):
    if len(name) > 7:
        return True
    return False

long_names = filter(is_name_long, names)
print(list(long_names))         # ['Asabeneh']

from functools import reduce

numbers_str = ['1', '2', '3', '4', '5']  # iterable
def add_two_nums(x, y):
    return int(x) + int(y)

total = reduce(add_two_nums, numbers_str)
print(total)    # 15

countries = ['Estonia', 'Finland', 'Sweden', 'Denmark', 'Norway', 'Iceland']
names = ['Asabeneh', 'Lidiya', 'Ermias', 'Abraham']
numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]