python_training_and_exercise_on_function

Python Training and Exercise on Function

Installing

Python 3.6 (The best is to use virtuall environment)

Topics

function intro
Built in functions
Key Words
Basic Custom Function
Passing Arguments to a Function
Call A Function
Return value
Keyword Arguments [Call the function by passing the name of the arguments]
Default Arguments
args and kwargs
Passing Collections to a Function
Functions - "First Class Citizens"
Mapping Functions in a Dictionary
Documentation

A function is a block of code that is reusable.

print
type ( check, compare, cast )

Built in functions

Key Words

def
pass
return

Basic Custom Function

def function_name(Arguments):
	# code

An Empty Function
Use print

Passing Arguments to a Function

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

Call A Function

add(5,6)

Return value

def add(a, b):
   return a + b
   
sum = add(5,6)
print(sum)

# sum = add(5+6+7) [error]

Keyword Arguments [Call the function by passing the name of the arguments]

def add(a, b):
   return a + b
   
sum = add(a=5,b=6)
print(sum)

sum = add(b=5,a=6)
print(sum)

Default Arguments

def add(a, b, c=0, d=5):
   return a + b + c + d
   
sum = add(5,6)
print(sum)

sum = add(5,6,7)
print(sum)
   
sum = add(a=5,b=6)
print(sum)

sum = add(b=5,a=6)
print(sum)

sum = add(b=5,a=6, d=7)
print(sum)

*args and **kwargs

You can set up functions to accept infinite arguments using *args and infinite keyword arguments, using *kwargs.

def args_kwargs(*args, **kwargs):
	print(args)
	print(kwargs)

args_kwargs(1,2,3,4,name='sharif', url='techsharif.com')

Scope

def function_a():
	a = 1
	b = 2
	return a+b
	
def function_b():
	c = 3
	return a+c
	
print( function_a() )
print( function_b() )

Global

def function_a():
	global a
	a = 1
	b = 2
	return a+b
	
def function_b():
	c = 3
	return a+c
	
print( function_a() )
print( function_b() )

Passing Collections to a Function

Basic Collection Concept

a = [1, 2, 3]
b = [4, 5, 6]

# statement 01
c = a+b
print(c)

# statement 02
c = a
c += b
print(c)

This is safe

 def no_side_effects(numbers):
     print(numbers)
     numbers = numbers + [11,12]
     print(numbers)
	 
some_numbers = [1,2,3,4,5]
no_side_effects(some_numbers)
print(some_numbers)

This is also safe if you know this

 def with_side_effects(numbers):
     print(numbers)
     numbers += numbers + [11,12]
     print(numbers)
	 
some_numbers = [1,2,3,4,5]
with_side_effects(some_numbers)
print(some_numbers)

Functions - "First Class Citizens"

Passing Functions to a Function

def inner_call(x):
    return f'{x}'

def outer_call(inner_call,x):
    return inner_call(x)

print outer_call(inner_call,10)

Nested Function

def outer_call(text):
    def inner_call(t):
        return t.lower() + '...'
    return inner_call(text)

print (outer_call('Hello, World'))

Mapping Functions in a Dictionary

def add(a,b):
   retuen a+b
   
def sub(a,b):
   retuen a-b

function_dict = {'add':add, 'sub':sub}
print(add(5,6))
print(function_dict['sub'](5,6))

lambda

add = lambda x, y : x + y
print( add(3,4) )

Recursion

def fun():
	fun()

Documentation

def complex(real=0.0, imag=0.0):
    """Form a complex number.

    Keyword arguments:
    real -- the real part (default 0.0)
    imag -- the imaginary part (default 0.0)
	
	Return:
	Complex number based on real and imag
    """
    if imag == 0.0 and real == 0.0:
        return complex_zero

Exercise

Take a input. If the type of the input value is either int or float, you should print the absolute value of the function input. Otherwise, print "Nope"

First, def a function called squere that takes an argument called number.
Make that function return the squere of that number (i.e. that number multiplied by itself).
Define a second function called by_two that takes an argument called number. if that number is divisible by 2 ,by_two should call squere(number) and return its result. Otherwise, by_two should return False. -Check if it works.

Write a function named word_frequency to find number of occurrences of each word in a dictionary. word_frequency(['a', 'b', 'a']) = {'a': 2, 'b': 1}

Extra Link

Author

Sharif Chowdhury - techsharif

techsharif/python_training_and_exercise_on_function.md