Python has many built-in and external libraries that serve different purposes—like working with dates, math, web, files, images, data science, AI, and more.

Below is a categorized list of popular Python libraries, along with a small example for each.

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🧮 1. Standard (Built-in) Libraries

These come pre-installed with Python.

Library	Purpose	Example
calendar	Date calendar generation	calendar.month(2025, 6)
datetime	Working with dates & times	datetime.now()
math	Math functions	math.sqrt(16)
random	Random number generation	random.randint(1, 10)
os	Interact with OS (files, dirs)	os.listdir()
sys	System-specific params/functions	sys.exit()
json	Working with JSON data	json.dumps({"name": "Akshit"})
re	Regular expressions	re.search("a", "apple")
time	Time-related functions	time.sleep(2)
statistics	Stats functions	statistics.mean([1, 2, 3])
itertools	Iterators (combinations, permutations)	itertools.permutations([1, 2])

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📦 2. External Libraries (Need installation using pip)

📊 Data Science & Machine Learning

Library	Purpose	Example
numpy	Numeric arrays, math ops	np.array([1,2,3])
pandas	DataFrames & data handling	pd.read_csv("data.csv")
matplotlib	Plotting graphs	plt.plot([1,2,3])
seaborn	Advanced data visualization	sns.histplot(data)
scikit-learn	ML algorithms	model.fit(X, y)
tensorflow	Deep learning	tf.constant([1,2])
keras	Neural networks	model = keras.Sequential()
xgboost	Gradient boosting	xgboost.train()

📊 Example:

import numpy as np
a = np.array([1, 2, 3])
print(a.mean())

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🌐 Web Development

Library	Purpose	Example
flask	Micro web framework	Flask(__name__)
django	Full web framework	python manage.py runserver
requests	HTTP requests	requests.get("https://api")
beautifulsoup4	Web scraping	BeautifulSoup(html, "html.parser")
selenium	Browser automation	webdriver.Chrome()

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🧠 AI / NLP / Chatbot

Library	Purpose	Example
nltk	Natural Language Processing	nltk.word_tokenize(text)
spacy	NLP + Named Entity Recognition	spacy.load("en_core_web_sm")
transformers	Pretrained models from HuggingFace	pipeline("text-generation")

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📁 File Handling / Utilities

Library	Purpose	Example
openpyxl	Read/write Excel files	load_workbook("file.xlsx")
csv	Work with CSV files	csv.reader(open("file.csv"))
shutil	File operations	shutil.copy("a.txt", "b.txt")
zipfile	Zip files	zipfile.ZipFile('a.zip')

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🔐 Cybersecurity / Encryption

Library	Purpose	Example
hashlib	Hashing	hashlib.sha256(b"hello")
cryptography	Encryption	Fernet(key).encrypt()

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📷 Images / Audio / Video

Library	Purpose	Example
Pillow	Image handling	Image.open("img.jpg")
opencv	Computer vision	cv2.imread("img.jpg")
pyaudio	Audio recording	pyaudio.Stream()
moviepy	Video editing	VideoFileClip("video.mp4")

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🧰 Other Useful Libraries

Library	Purpose	Example
argparse	Command-line arguments	argparse.ArgumentParser()
logging	Logs and debugging	logging.info("test")
tkinter	GUI building	tk.Tk()
threading	Multithreading	threading.Thread()
multiprocessing	Multi-core processing	Process(target=func)
dotenv	Environment variables	load_dotenv()
pyttsx3	Text to speech	pyttsx3.init().say("Hi")
speechrecognition	Convert speech to text	recognizer.recognize_google(audio)

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🧪 BONUS: Install Any External Library

pip install <library-name>

Example:

pip install numpy

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