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Installing & Using External Libraries in Python with `pip`

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Learn how to install and use external Python libraries with pip – a beginner-friendly guide with practical examples. Discover essential pip commands, popular libraries like requests, matplotlib, and beautifulsoup4, and best practices for dependency management.

What is pip?

pip is the standard package manager for Python that allows you to install and manage additional libraries that aren’t part of the standard Python library.

Checking if pip is Installed

Before using pip, check if it’s already installed (it usually comes with Python 3.4+):

pip --version

or

pip3 --version

Basic pip Commands

Installing a Package

pip install package_name

Example:

pip install requests

Installing a Specific Version

pip install package_name==version_number

Example:

pip install requests==2.25.1

Upgrading a Package

pip install --upgrade package_name

Example:

pip install --upgrade requests

Uninstalling a Package

pip uninstall package_name

Example:

pip uninstall requests

Listing Installed Packages

pip list

Showing Package Information

pip show package_name

Example:

pip show requests

Practical Examples of Using External Libraries

Example 1: Making HTTP Requests with requests

import requests

# Make a GET request to a website
response = requests.get('https://www.example.com')

# Check if the request was successful
if response.status_code == 200:
    print("Successfully fetched the page!")
    print(f"Page content length: {len(response.text)} characters")
else:
    print(f"Failed to fetch page. Status code: {response.status_code}")

Example 2: Working with Dates using python-dateutil

from dateutil import parser
from dateutil.relativedelta import relativedelta

# Parse a date string
date = parser.parse("June 5th 2023 10:30 PM")
print(f"Parsed date: {date}")

# Add 2 months to the date
new_date = date + relativedelta(months=+2)
print(f"Date after adding 2 months: {new_date}")

Example 3: Data Visualization with matplotlib

import matplotlib.pyplot as plt

# Sample data
x = [1, 2, 3, 4, 5]
y = [2, 4, 6, 8, 10]

# Create a simple line plot
plt.plot(x, y)

# Add labels and title
plt.xlabel('X Axis')
plt.ylabel('Y Axis')
plt.title('Simple Line Plot')

# Display the plot
plt.show()

Example 4: Working with Excel Files using openpyxl

from openpyxl import Workbook

# Create a new Excel workbook
wb = Workbook()

# Get the active worksheet
ws = wb.active

# Add some data
ws['A1'] = "Name"
ws['B1'] = "Age"
ws['A2'] = "Alice"
ws['B2'] = 25
ws['A3'] = "Bob"
ws['B3'] = 30

# Save the workbook
wb.save("sample.xlsx")
print("Excel file created successfully!")

Example 5: Web Scraping with beautifulsoup4

import requests
from bs4 import BeautifulSoup

# Fetch a webpage
url = 'https://en.wikipedia.org/wiki/Python_(programming_language)'
response = requests.get(url)

# Parse the HTML content
soup = BeautifulSoup(response.text, 'html.parser')

# Extract and print the page title
title = soup.find('h1').text
print(f"Page title: {title}")

# Extract and print the first paragraph
first_paragraph = soup.find('p').text
print(f"\nFirst paragraph:\n{first_paragraph}")

Virtual Environments (Bonus)

For project-specific dependencies, it’s good practice to use virtual environments:

  1. Create a virtual environment: 
    python -m venv myenv
  2. Activate it:
    • On Windows: 
      myenv\Scripts\activate
    • On macOS/Linux: 
      source myenv/bin/activate
  3. Now install packages within this environment: 
    pip install package_name
  4. Deactivate when done: 
    deactivate

Requirements Files

You can save all your project’s dependencies to a file:

pip freeze > requirements.txt

And later install them all at once:

pip install -r requirements.txt

Conclusion

Using external libraries with pip greatly expands what you can do with Python. Start with simple libraries like requests or matplotlib, and gradually explore more specialized ones as you need them for your projects.