Python Modules

In this article, we will cover all about Python modules, such as How to create our own simple module, Import Python modules, From statements in Python, how we can use the alias to rename the module, etc.

What is Python Module

A Python module is a file containing Python definitions and statements. A module can define functions, classes, and variables. A module can also include runnable code. Grouping related code into a module makes the code easier to understand and use. It also makes the code logically organized.

Create a Python Module

Let’s create a simple calc.py in which we define two functions, one add and another subtract.

Python3

# A simple module, calc.py
def add(x, y):
    return (x+y)

def subtract(x, y):
    return (x-y)

Import module in Python

We can import the functions, and classes defined in a module to another module using the import statement in some other Python source file.

When the interpreter encounters an import statement, it imports the module if the module is present in the search path. A search path is a list of directories that the interpreter searches for importing a module. For example, to import the module calc.py, we need to put the following command at the top of the script.

Syntax of Python Import

import module

Note: This does not import the functions or classes directly instead imports the module only. To access the functions inside the module the dot(.) operator is used.

Importing modules in Python Example

Now, we are importing the calc that we created earlier to perform add operation.

Python3

# importing  module calc.py
import calc

print(calc.add(10, 2))

Output:

12

Python Import From Module

Python’s from statement lets you import specific attributes from a module without importing the module as a whole.

Import Specific Attributes from a Python module

Here, we are importing specific sqrt and factorial attributes from the math module.

Python3

# importing sqrt() and factorial from the
# module math
from math import sqrt, factorial

# if we simply do "import math", then
# math.sqrt(16) and math.factorial()
# are required.
print(sqrt(16))
print(factorial(6))

Output: 

4.0
720

Import all Names 

The * symbol used with the import statement is used to import all the names from a module to a current namespace.

Syntax:

from module_name import *

What does import * do in Python

The use of * has its advantages and disadvantages. If you know exactly what you will be needing from the module, it is not recommended to use *, else do so.

Python3

# importing sqrt() and factorial from the
# module math
from math import *

# if we simply do "import math", then
# math.sqrt(16) and math.factorial()
# are required.
print(sqrt(16))
print(factorial(6))

Output

4.0
720

Locating Python Modules

Whenever a module is imported in Python the interpreter looks for several locations. First, it will check for the built-in module, if not found then it looks for a list of directories defined in the sys.path. Python interpreter searches for the module in the following manner –

• First, it searches for the module in the current directory.
• If the module isn’t found in the current directory, Python then searches each directory in the shell variable PYTHONPATH. The PYTHONPATH is an environment variable, consisting of a list of directories.
• If that also fails python checks the installation-dependent list of directories configured at the time Python is installed.

Directories List for Modules

Here, sys.path is a built-in variable within the sys module. It contains a list of directories that the interpreter will search for the required module.

Python3

# importing sys module
import sys

# importing sys.path
print(sys.path)

Output:

[‘/home/nikhil/Desktop/gfg’, ‘/usr/lib/python38.zip’, ‘/usr/lib/python3.8’, ‘/usr/lib/python3.8/lib-dynload’, ”, ‘/home/nikhil/.local/lib/python3.8/site-packages’, ‘/usr/local/lib/python3.8/dist-packages’, ‘/usr/lib/python3/dist-packages’, ‘/usr/local/lib/python3.8/dist-packages/IPython/extensions’, ‘/home/nikhil/.ipython’]

Renaming the Python module

We can rename the module while importing it using the keyword.

Syntax:  Import Module_name as Alias_name

Python3

# importing sqrt() and factorial from the
# module math
import math as mt

# if we simply do "import math", then
# math.sqrt(16) and math.factorial()
# are required.
print(mt.sqrt(16))
print(mt.factorial(6))

Output

4.0
720

Python Built-in modules

There are several built-in modules in Python, which you can import whenever you like.

Python3

# importing built-in module math
import math

# using square root(sqrt) function contained
# in math module
print(math.sqrt(25))

# using pi function contained in math module
print(math.pi)

# 2 radians = 114.59 degrees
print(math.degrees(2))

# 60 degrees = 1.04 radians
print(math.radians(60))

# Sine of 2 radians
print(math.sin(2))

# Cosine of 0.5 radians
print(math.cos(0.5))

# Tangent of 0.23 radians
print(math.tan(0.23))

# 1 * 2 * 3 * 4 = 24
print(math.factorial(4))

# importing built in module random
import random

# printing random integer between 0 and 5
print(random.randint(0, 5))

# print random floating point number between 0 and 1
print(random.random())

# random number between 0 and 100
print(random.random() * 100)

List = [1, 4, True, 800, "python", 27, "hello"]

# using choice function in random module for choosing
# a random element from a set such as a list
print(random.choice(List))


# importing built in module datetime
import datetime
from datetime import date
import time

# Returns the number of seconds since the
# Unix Epoch, January 1st 1970
print(time.time())

# Converts a number of seconds to a date object
print(date.fromtimestamp(454554))

Output:

5.0
3.14159265359
114.591559026
1.0471975512
0.909297426826
0.87758256189
0.234143362351
24
3
0.401533172951
88.4917616788
True
1461425771.87