Practical recipes for building LLM applications with LangChain: prompts, chains, agents, memory, and RAG. Installation 1# Core LangChain 2pip install langchain langchain-community langchain-core 3 4# OpenAI 5pip install langchain-openai 6 7# Other providers 8pip install langchain-anthropic # Claude 9pip install …

Essential patterns for working with Pandas DataFrames: creation, manipulation, filtering, aggregation, and transformation. Installation 1pip install pandas numpy Creating DataFrames From Dictionary 1import pandas as pd 2import numpy as np 3 4# From dict of lists 5df = pd.DataFrame({ 6 'name': ['Alice', …

Comprehensive guide to Random Forests: theory, implementation, tuning, and interpretation. What are Random Forests? Random Forest is an ensemble learning method that constructs multiple decision trees and combines their predictions. Key Concepts: Bagging: Bootstrap Aggregating - train each tree on random subset of data …

Common patterns and workflows for scikit-learn: preprocessing, model training, evaluation, and pipelines. Installation 1pip install scikit-learn numpy pandas matplotlib Basic Workflow 1from sklearn.model_selection import train_test_split 2from sklearn.preprocessing import StandardScaler 3from sklearn.linear_model …

Click is a Python package for creating beautiful command-line interfaces with minimal code. Uses decorators for a clean, composable API. Powers Flask, AWS CLI, and many other tools. Use Case Use Click when you need to: Build CLI tools in Python Create nested command groups Handle complex option parsing Generate …

Virtual environments isolate Python project dependencies, preventing conflicts between projects. Essential for reproducible research and clean dependency management. Use Case Use virtual environments when you need to: Isolate project dependencies Work on multiple projects with different requirements Ensure reproducible …

A simple decorator to measure and print the execution time of any function. Useful for quick performance profiling during development. Use Case Use this when you want to quickly measure how long a function takes to execute without setting up complex profiling tools. Perfect for identifying slow functions during …

High-level Keras API for building neural networks quickly. Installation 1# Keras is included in TensorFlow 2.x 2pip install tensorflow 3 4# Standalone Keras (multi-backend) 5pip install keras Sequential Model 1from tensorflow import keras 2from tensorflow.keras import layers 3 4model = keras.Sequential([ 5 …

pip - Package installer for Python. Basic Commands 1# Install package 2pip install package-name 3 4# Install specific version 5pip install package-name==1.0.0 6 7# Install minimum version 8pip install 'package-name>=1.0.0' 9 10# Install version range 11pip install 'package-name>=1.0.0,<2.0.0' …

Common code smells in Python and how to fix them. Mutable Default Arguments 1# ❌ Bad: Mutable default argument 2def append_to_list(item, my_list=[]): 3 my_list.append(item) 4 return my_list 5 6print(append_to_list(1)) # [1] 7print(append_to_list(2)) # [1, 2] - Unexpected! 8 9# ✅ Good: Use None as default 10def …

Secure coding practices for Python applications. SQL Injection Prevention 1# ❌ Vulnerable 2user_input = request.GET['username'] 3query = f"SELECT * FROM users WHERE username = '{user_input}'" 4cursor.execute(query) 5 6# ✅ Secure: Parameterized queries 7user_input = …