Why Developers Choose the 22 Most Downloaded Python Packages

Introduction

The following list starts from the most downloaded Python packages on PyPI over the past year, explores their purposes, relationships, and why they are so popular among developers worldwide.

1. urllib3

Downloads: 893 million urllib3 is an HTTP client that adds many features missing from the Python standard library, such as thread safety, connection pooling, SSL/TLS verification, chunked transfer encoding, retry helpers, gzip/deflate support, and HTTP/SOCKS proxy support.

Despite its name, urllib3 is not a successor to urllib2; for core functionality use urllib.request.

For most end‑users, the requests package (see entry #6) is recommended because it depends on urllib3 and provides a simpler API.

2. six

Downloads: 732 million six is a compatibility library for writing code that runs on both Python 2 and Python 3. It offers helper functions that smooth over syntax differences, e.g., six.print_() works on both versions.

The name comes from 2 × 3 = 6.

See also the future package for similar functionality.

For pure Python 3 code, use 2to3 to migrate.

3. botocore, boto3, s3transfer, awscli

These four projects are tightly related:

botocore (660 million downloads) – low‑level AWS interface.

s3transfer (584 million downloads) – manages Amazon S3 transfers.

awscli (394 million downloads) – command‑line interface built on botocore.

boto3 (329 million downloads) – high‑level AWS SDK built on botocore.

Botocore underpins Boto3 and the AWS CLI, illustrating AWS’s dominance in the Python ecosystem.

4. pip

Downloads: 627 million pip ("Pip Installs Packages") is the standard Python package installer. It can install packages from PyPI, private indexes, or local mirrors.

Install: pip install <package> Uninstall: pip uninstall <package> Export requirements: pip freeze > requirements.txt Works well with virtualenv to create isolated environments.

5. python-dateutil

Downloads: 617 million

The python-dateutil module extends the standard datetime library with powerful parsing, relative deltas, and timezone handling.

Example of fuzzy date parsing:

from dateutil.parser import parse
logline = 'INFO 2020-01-01T00:00:01 Happy new year, human.'
timestamp = parse(logline, fuzzy=True)
print(timestamp)  # 2020-01-01 00:00:01

6. requests

Downloads: 611 million

Built on top of urllib3, requests makes HTTP requests extremely simple.

import requests
r = requests.get('https://api.github.com/user', auth=('user', 'pass'))
print(r.status_code)      # 200
print(r.headers['content-type'])  # application/json; charset=utf8
print(r.text)
print(r.json())

7. s3transfer

Downloads: 370 million

Provides the transfer manager used by boto3 and the AWS CLI. Its API may change between minor versions, so it is usually used indirectly via higher‑level libraries.

8. certifi

Downloads: 552 million certifi supplies a curated collection of root SSL certificates, allowing Python code to verify HTTPS connections just like modern browsers.

9. idna

Downloads: 527 million

Implements the Internationalized Domain Name (IDNA) protocol defined in RFC 5891, providing idna.encode() and idna.decode() for converting Unicode domain names to ASCII punycode and back.

import idna
print(idna.encode('ドメイン.テスト'))  # b'xn--eckwd4c7c.xn--zckzah'
print(idna.decode('xn--eckwd4c7c.xn--zckzah'))  # ドメイン.テスト

10. PyYAML

Downloads: 525 million

YAML is a human‑readable data serialization format. PyYAML parses and emits YAML, supporting complex Python objects.

11. pyasn1

Downloads: 512 million

Pure‑Python implementation of ASN.1 types and DER/BER/CER encoding, used by many security‑related packages (e.g., certifi).

12. docutils

Downloads: 508 million

Modular system for converting plain text (reStructuredText) into formats like HTML, XML, and LaTeX. It powers the Python documentation and Sphinx.

13. chardet

Downloads: 501 million

Detects the character encoding of byte streams. It is a dependency of requests and many other packages.

chardetect somefile.txt
# ascii with confidence 1.0

14. rsa

Downloads: 492 million

Pure‑Python RSA implementation supporting encryption/decryption, signing/verification, and PKCS#1 v1.5 key generation.

import rsa
(bob_pub, bob_priv) = rsa.newkeys(512)
crypto = rsa.encrypt('hello Bob!', bob_pub)
message = rsa.decrypt(crypto, bob_priv)
print(message.decode('utf8'))  # hello Bob!

15. jmespath

Downloads: 473 million

Provides a declarative way to extract data from JSON structures.

import jmespath
d = {"foo": {"bar": "baz"}}
print(jmespath.search('foo.bar', d))  # baz

d = {"foo": {"bar": [{"name": "one"}, {"name": "two"}]}}
print(jmespath.search('foo.bar[*].name', d))  # ['one', 'two']

16. setuptools

Downloads: 401 million

Tool for creating and distributing Python packages. Documentation can be found at packaging.python.org .

17. awscli

Part of the AWS‑related group (see #3, #7, #22).

18. pytz

Downloads: 394 million

Provides accurate and cross‑platform timezone definitions.

from datetime import datetime
from pytz import timezone
amsterdam = timezone('Europe/Amsterdam')
ams_time = amsterdam.localize(datetime(2002, 10, 27, 6, 0, 0))
print(ams_time)  # 2002-10-27 06:00:00+01:00

19. futures

Downloads: 389 million

Backport of the concurrent.futures module for Python 2. Provides a simple thread‑pool interface.

from concurrent.futures import ThreadPoolExecutor
from time import sleep

def return_after_5_secs(msg):
    sleep(5)
    return msg

pool = ThreadPoolExecutor(3)
future = pool.submit(return_after_5_secs, "Hello world")
print(future.done())  # False
sleep(5)
print(future.done())  # True
print(future.result())  # Hello world

20. colorama

Downloads: 370 million

Adds cross‑platform colored terminal text.

from colorama import Fore, Back, Style
print(Fore.RED + 'some red text')
print(Back.GREEN + 'and with a green background')
print(Style.DIM + 'and in dim text')
print(Style.RESET_ALL)
print('back to normal now')

21. simplejson

Downloads: 341 million

A faster, more feature‑rich drop‑in replacement for the built‑in json module, with optional C acceleration.

22. boto3

Part of the AWS‑related group (see #3, #7, #17).

Conclusion

The top 22 packages reveal several themes: many provide core functionality such as time handling, configuration, encryption, and networking; most are heavily depended upon by other projects; and a few serve as tooling for packaging, documentation, and compatibility. Understanding these libraries helps developers make informed choices when building Python applications.