While learning programming and reading some resources you'd have come across this word 'abstraction' which simply means to reduce and reuse the code as much as possible.

Functions and Modules facilitate abstraction. You create functions when you want to do something repeatedly within a file.

Modules come into picture when you want to reuse a group of functions in different source files. Modules are also useful in structuring the program well.

• Using Standard Libraries and other third party modules:
• Structuring the program

Example: You can read about the methods/functions of all the standard libraries in the official Python Docs in detail.

import time
for i in range(100):
    time.sleep(1)   # Waits for 1 second and then executes the next command
    print(str(i) + ' seconds have passed')  # prints the number of seconds passed after the program was started

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# To calculate the execution time of a part of program
import time
start = time.time()
# code here
end = time.time()
print('Execution time:' , end-start)

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# Using math Module
import math
print(math.sqrt(100))   # prints 10

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Third party modules don't come bundled with python , but we have to install it externally using package managers like pip and easy install

# To make http requests
import requests
rq = requests.get(target_url)
print(rq.status_code)

Find out more about python-requests module here

We want to make a program that has various functions regarding prime numbers. So lets start. We will define all the functions in prime_functions.py

# prime_functions.py
from math import ceil, sqrt
def isPrime(a):
    if a == 2:
        return True
    elif a % 2 == 0:
        return False
    else:
        for i in range(3,ceil(sqrt(a)) + 1,2):
            if a % i == 0:
                return False
        return True

def print_n_primes(a):
    i = 0
    m = 2
    while True:
        if isPrime(m) ==True:
            print(m)
            i += 1
        m += 1
        if i == a:
            break

Now we want to use the functions that we just created in prime_functions.py so we create a new file playground.py to use those functions.

Please note that this program is far too simple to make two separate files, it is just to demonstrate. But when there are large complex programs, making different files is really useful.

# playground.py
import prime_functions
print(prime_functions.isPrime(29)) # returns True