A programmer usually prefer the predefined functions and variables for document,
Modules are collection of several diffrent definitions(functions and variables)
and statements.Or to put simply The files with ".py" appended at the name of the
source code,the user can import that module(files) or specific function fromthat
module into the file.
programmer use the module,complete project in less time and more efficient way.
programmer generally import either the module which user saved with ".py" or can
use some standard module like random,queue,array,math,profile,statistics etc....
just type "help('modules')" and you can see all standard modules in interactive
mode.
------------------------------------------------------------------------------- Eg--> # here entire math universe will come into the program
>>> import math
>>> math.cos(60)# math.cos()
-0.9524129804151563
>>> math.ceil(6.12)#math.ceil()
7
>>> math.log2(4)#math.log2()
2.0
-------------------------------------------------------------------------------
#but if you want specific built in function then use "from". Eg--> # only perticular function will come from the math module.
>>> from math import sqrt,sin
>>> sqrt(9)#math module will be undefine since only function sqrt,sin defined
3.0
>>> sin(60)# sin is imported from math and "math." is not required
-0.3048106211022167
>>> cos(60)# cos is not part of the built in function that imported from math.
'''Traceback (most recent call last): File "<pyshell#3>", line 1, in <module> cos(60)
NameError: name 'cos' is not defined'''
>>> math.cos(60)# this gives error because math has not been imported
'''Traceback (most recent call last): File "<pyshell#4>", line 1, in <module> math.cos(60)
NameError: name 'math' is not defined'''
-------------------------------------------------------------------------------

import numpy as np:

import pyttsx3 # using ptython to convert text to speech 

#use import statement to import modules
import random
r = random.randint(1,10)
#use from-import statements to import functions
from random import randint
r = randint(1,10)
#use from module import * statement to import all functions
from random import *
r = randint(1,10)

import pandas as pd:

# Python program to illustrate
# math module
import math
  
def Main():
    num = -85
  
    # fabs is used to get the absolute 
    # value of a decimal
    num = math.fabs(num) 
    print(num)
      
      
if __name__=="__main__":
    Main()

from numpy import exp, array, random, dot
training_set_inputs = array([[0, 0, 1], [1, 1, 1], [1, 0, 1], [0, 1, 1]])
training_set_outputs = array([[0, 1, 1, 0]]).T
random.seed(1)
synaptic_weights = 2 * random.random((3, 1)) - 1
for iteration in xrange(10000): output = 1 / (1 + exp(-(dot(training_set_inputs, synaptic_weights)))) synaptic_weights += dot(training_set_inputs.T, (training_set_outputs - output) * output * (1 - output))
print 1 / (1 + exp(-(dot(array([1, 0, 0]), synaptic_weights))))

'''
Please note that there are many more that I may not have listed
There are also other reasons for using these modules other than the
reasons that I have listed.
'''
import random # Mainly used for random number
import time # Mainly used for time.sleep()
import math # More complex maths
import os # Working with files?
import pygame # Creating windows (games)
import turtle # Creating windows
import re # Regex
import numpy # Dealing with arrays
import socket # Netorking, communicating between computers
import this # Poem
import keyboard # Receiving keyboard inputs
import mouse # Detecting mouse clicks
import webbrowser # Opening websites
import pprint # Formating text
import pyautogui # Automation
# Might add more