Python in 30 Days: Day 12 – Modules

What is a module?

A module is a file containing a set of codes or a set of functions that can be included in an application. A module could be a file containing a single variable, a function, or a big code base.

Creating a Module

To create a module, we write our code in a Python script and save it as a.py file. Create a file named mymodule.py inside your project folder. Let us write some code in this file.

# mymodule.py file
def generate_full_name(firstname, lastname):
    return firstname + ' ' + lastname

Create a main.py file in your project directory and import the mymodule.py file.

Importing a Module

To import the file we use the import keyword and the name of the file only.

# main.py file
import mymodule
print(mymodule.generate_full_name('Tech', 'G')) # Tech G

Import Functions from a Module

We can have many functions in a file and we can import all the functions differently.

# main.py file
from mymodule import generate_full_name, sum_two_nums, person, gravity
print(generate_full_name('Tech','G'))
print(sum_two_nums(1,9))
mass = 100;
weight = mass * gravity
print(weight)
print(person['firstname'])

Import Functions from a Module and Renaming

During importing we can rename the name of the module.

# main.py file
from mymodule import generate_full_name as fullname, sum_two_nums as total, person as p, gravity as g
print(fullname('Tech','G'))
print(total(1, 9))
mass = 100;
weight = mass * g
print(weight)
print(p)
print(p['firstname'])

Import Built-in Modules

Like other programming languages, we can also import modules by importing the file/function using the keyword import. Let’s import the common module we will use most of the time. Some of the common built-in modules: math, datetime, os,sys, random, statistics, collections, json,re

OS Module

Using the Python OS module it is possible to automatically perform many operating system tasks. The OS module in Python provides functions for creating, changing the current working directory, and removing a directory (folder), fetching its contents, changing and identifying the current directory.

# import the module
import os
# Creating a directory
os.mkdir('directory_name')
# Changing the current directory
os.chdir('path')
# Getting current working directory
os.getcwd()
# Removing directory
os.rmdir()

Sys Module

The sys module provides functions and variables used to manipulate different parts of the Python runtime environment. Function sys.argv returns a list of command line arguments passed to a Python script. The item at index 0 in this list is always the name of the script, at index 1 is the argument passed from the command line.

Example of a script.py file:

import sys
#print(sys.argv[0], argv[1],sys.argv[2])  # this line would print out: filename argument1 argument2
print('Welcome {}. Enjoy  {} challenge!'.format(sys.argv[1], sys.argv[2]))

Now to check how this script works I wrote in a command line:

python script.py Tech Python in 30 Days

The result:

Welcome Tech. Enjoy Python in 30 Days challenge!

Some useful sys commands:

# to exit sys
sys.exit()
# To know the largest integer variable it takes
sys.maxsize
# To know environment path
sys.path
# To know the version of python you are using
sys.version

Statistics Module

The statistics module provides functions for mathematical statistics of numeric data. The popular statistical functions which are defined in this module: mean, median, mode, stdev etc.

from statistics import * # importing all the statistics modules
ages = [20, 20, 4, 24, 25, 22, 26, 20, 23, 22, 26]
print(mean(ages))       # ~22.9
print(median(ages))     # 23
print(mode(ages))       # 20
print(stdev(ages))      # ~2.3

Math Module

Module containing many mathematical operations and constants.

import math
print(math.pi)           # 3.141592653589793, pi constant
print(math.sqrt(2))      # 1.4142135623730951, square root
print(math.pow(2, 3))    # 8.0, exponential function
print(math.floor(9.81))  # 9, rounding to the lowest
print(math.ceil(9.81))   # 10, rounding to the highest
print(math.log10(100))   # 2, logarithm with 10 as base

Now, we have imported the math module which contains lots of function which can help us to perform mathematical calculations. To check what functions the module has got, we can use help(math), or dir(math). This will display the available functions in the module. If we want to import only a specific function from the module we import it as follows:

from math import pi
print(pi)

It is also possible to import multiple functions at once

from math import pi, sqrt, pow, floor, ceil, log10
print(pi)                 # 3.141592653589793
print(sqrt(2))            # 1.4142135623730951
print(pow(2, 3))          # 8.0
print(floor(9.81))        # 9
print(ceil(9.81))         # 10
print(math.log10(100))    # 2

But if we want to import all the function in math module we can use * .

from math import *
print(pi)                  # 3.141592653589793, pi constant
print(sqrt(2))             # 1.4142135623730951, square root
print(pow(2, 3))           # 8.0, exponential
print(floor(9.81))         # 9, rounding to the lowest
print(ceil(9.81))          # 10, rounding to the highest
print(math.log10(100))     # 2

When we import we can also rename the name of the function.

from math import pi as  PI
print(PI) # 3.141592653589793

String Module

A string module is a useful module for many purposes. The example below shows some use of the string module.

import string
print(string.ascii_letters) # abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ
print(string.digits)        # 0123456789
print(string.punctuation)   # !"#$%&'()*+,-./:;<=>?@[\]^_`{|}~

Random Module

By now you are familiar with importing modules. Let us do one more import to get very familiar with it. Let us import random module which gives us a random number between 0 and 0.9999…. The random module has lots of functions but in this section we will only use random and randint.

from random import random, randint
print(random())   # it doesn't take any arguments; it returns a value between 0 and 0.9999
print(randint(5, 20)) # it returns a random integer number between [5, 20] inclusive

Now do some exercises for your brain and muscles.

Exercises: Python in 30 Days: Day 12 – Modules

Exercises: Level 1

Writ a function which generates a six digit/character random_user_id.
```
  print(random_user_id());
  '1ee33d'
```
Modify the previous task. Declare a function named user_id_gen_by_user. It doesn’t take any parameters but it takes two inputs using input(). One of the inputs is the number of characters and the second input is the number of IDs which are supposed to be generated.

print(user_id_gen_by_user()) # user input: 5 5
#output:
#kcsy2
#SMFYb
#bWmeq
#ZXOYh
#2Rgxf
   
print(user_id_gen_by_user()) # 16 5
#1GCSgPLMaBAVQZ26
#YD7eFwNQKNs7qXaT
#ycArC5yrRupyG00S
#UbGxOFI7UXSWAyKN
#dIV0SSUTgAdKwStr

Write a function named rgb_color_gen. It will generate rgb colors (3 values ranging from 0 to 255 each).

print(rgb_color_gen())
# rgb(125,244,255) - the output should be in this form

Exercises: Level 2

Write a function list_of_hexa_colors which returns any number of hexadecimal colors in an array (six hexadecimal numbers written after #. Hexadecimal numeral system is made out of 16 symbols, 0-9 and first 6 letters of the alphabet, a-f. Check the task 6 for output examples).
Write a function list_of_rgb_colors which returns any number of RGB colors in an array.
Write a function generate_colors which can generate any number of hexa or rgb colors.

   generate_colors('hexa', 3) # ['#a3e12f','#03ed55','#eb3d2b'] 
   generate_colors('hexa', 1) # ['#b334ef']
   generate_colors('rgb', 3)  # ['rgb(5, 55, 175','rgb(50, 105, 100','rgb(15, 26, 80'] 
   generate_colors('rgb', 1)  # ['rgb(33,79, 176)']

Exercises: Level 3

Call your function shuffle_list, it takes a list as a parameter and it returns a shuffled list
Write a function which returns an array of seven random numbers in a range of 0-9. All the numbers must be unique.

<< Day 11 | Day 13 >>