Importing Libraries in Python

What is a Library?

A library is a collection of reusable functions, classes, and modules. Python comes with many built-in libraries, and you can also use external libraries created by the Python community.

Importing Built-in Libraries

import math
print(“Square root of 16 is:”, math.sqrt(16))

Output:
Square root of 16 is: 4.0

Importing with an Alias

Use as to assign a shortcut to long library names.

import datetime as dt
today = dt.date.today()
print("Today’s date is:", today)

Output:
Today’s date is: 2025-05-24

Import Specific Parts of a Library

You can import only the functions you need.

from math import pi, pow
print("Pi is:", pi)
print("2 raised to 3 is:", pow(2, 3)) 

Output:

Pi is: 3.141592653589793
2 raised to 3 is: 8.0

Installing and Importing External Libraries

Libraries like pandas, numpy, and matplotlib are not built-in. You need to install them using pip, Python’s package manager.

Open your terminal or command prompt and run:

pip install pandas

Once installed, you can import and use it.

import pandas as pd
data = {'Name': ['John', 'Alice'], 'Age': [25, 30]}
df = pd.DataFrame(data)
print(df)

Output:

Installing Multiple Libraries at Once

You can install several libraries in one command:

pip install numpy matplotlib seaborn

Using try-except with External Libraries

Handle errors if the library isn’t installed.

try:
import seaborn as sns
print("Seaborn is ready to use.")
except ImportError:
print("Seaborn is not installed.")

Output:
Seaborn is ready to use.

pip list

You’ll get a list like:

numpy 1.26.4
pandas 2.2.1
matplotlib 3.8.4

Importing Your Own Modules

Create your own .py file and import it.

file name- abc.py

def hello(name):
    return f"Hello, {name}!"

file name – main.py

import abc
print(abc.hello("Alex"))

Output:
Hello, Alex!

Common External Libraries :