Python Modules

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.

Example: create a simple module

Python3

# A simple module, calc.py

def add(x, y):
    return (x+y)

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

Import Module in Python –  Import statement

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

Syntax:

import module

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.

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.

Example: Importing modules in Python

Python3

# importing  module calc.py
import calc

print(calc.add(10, 2))

Output:

12

The from import Statement

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

Example: Importing specific attributes from the 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 – From import *  Statement

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

Syntax:

from module_name import *

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.

Example: Importing all names

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 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.

Example: Directories List for Modules

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’]

Importing and renaming module

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

Example: Renaming the module

Python3

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

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

Output

4.0
720

The dir() function

The dir() built-in function returns a sorted list of strings containing the names defined by a module. The list contains the names of all the modules, variables, and functions that are defined in a module.

Python3

#  Import built-in module  random
import  random
print(dir(random))

Output:

[‘BPF’, ‘LOG4’, ‘NV_MAGICCONST’, ‘RECIP_BPF’, ‘Random’, ‘SG_MAGICCONST’, ‘SystemRandom’, ‘TWOPI’, ‘_BuiltinMethodType’, ‘_MethodType’, ‘_Sequence’, ‘_Set’, ‘__all__’, ‘__builtins__’, ‘__cached__’, ‘__doc__’, ‘__file__’, ‘__loader__’, ‘__name__’, ‘__package__’, ‘__spec__’, ‘_acos’, ‘_bisect’, ‘_ceil’, ‘_cos’, ‘_e’, ‘_exp’, ‘_inst’, ‘_itertools’, ‘_log’, ‘_pi’, ‘_random’, ‘_sha512’, ‘_sin’, ‘_sqrt’, ‘_test’, ‘_test_generator’, ‘_urandom’, ‘_warn’, ‘betavariate’, ‘choice’, ‘choices’, ‘expovariate’, ‘gammavariate’, ‘gauss’, ‘getrandbits’, ‘getstate’, ‘lognormvariate’, ‘normalvariate’, ‘paretovariate’, ‘randint’, ‘random’, ‘randrange’, ‘sample’, ‘seed’, ‘setstate’, ‘shuffle’, ‘triangular’, ‘uniform’, ‘vonmisesvariate’, ‘weibullvariate’]

Code Snippet illustrating python built-in modules:

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