Agent skill
python-programming
Python fundamentals, data structures, OOP, and data science libraries (Pandas, NumPy). Use when writing Python code, data manipulation, or algorithm implementation.
Install this agent skill to your Project
npx add-skill https://github.com/pluginagentmarketplace/custom-plugin-ai-data-scientist/tree/main/skills/python-programming
SKILL.md
Python Programming for Data Science
Master Python from fundamentals to advanced data science applications.
Quick Start
Essential Libraries
import pandas as pd
import numpy as np
import matplotlib.pyplot as plt
import seaborn as sns
Data Manipulation
# Read data
df = pd.read_csv('data.csv')
# Explore
print(df.head())
print(df.info())
print(df.describe())
# Filter
df_filtered = df[df['age'] > 18]
# Group and aggregate
summary = df.groupby('category')['sales'].agg(['sum', 'mean', 'count'])
# Vectorized operations (FAST!)
df['new_col'] = df['col1'] * 2 # Instead of loops
Core Concepts
1. Data Structures
- Lists:
[1, 2, 3]- ordered, mutable - Dictionaries:
{'key': 'value'}- key-value pairs - Tuples:
(1, 2, 3)- immutable - Sets:
{1, 2, 3}- unique elements
2. List Comprehensions
# Instead of loops
squares = [x**2 for x in range(10)]
filtered = [x for x in data if x > 0]
3. NumPy Arrays
arr = np.array([1, 2, 3, 4, 5])
arr * 2 # [2, 4, 6, 8, 10]
arr.mean() # 3.0
4. Pandas DataFrames
df = pd.DataFrame({
'name': ['Alice', 'Bob'],
'age': [25, 30],
'salary': [50000, 60000]
})
Performance Tips
Vectorization over Loops (10-100x faster):
# Bad (slow)
result = []
for x in data:
result.append(x * 2)
# Good (fast)
result = np.array(data) * 2
Common Patterns
Reading Files
# CSV
df = pd.read_csv('file.csv')
# Excel
df = pd.read_excel('file.xlsx', sheet_name='Sheet1')
# JSON
df = pd.read_json('file.json')
# SQL
import sqlite3
conn = sqlite3.connect('database.db')
df = pd.read_sql_query("SELECT * FROM table", conn)
Missing Data
df.dropna() # Remove rows
df.fillna(0) # Fill with value
df.fillna(df.mean()) # Fill with mean
Merging Data
# Join DataFrames
merged = pd.merge(df1, df2, on='id', how='left')
# Concatenate
combined = pd.concat([df1, df2], axis=0)
Best Practices
- Use vectorized operations
- Optimize data types
- Avoid loops when possible
- Use built-in functions
- Profile before optimizing
Troubleshooting
Common Issues
Problem: MemoryError with large DataFrames
# Solution 1: Use chunking
for chunk in pd.read_csv('large.csv', chunksize=10000):
process(chunk)
# Solution 2: Optimize dtypes
df['int_col'] = df['int_col'].astype('int32') # Instead of int64
df['cat_col'] = df['cat_col'].astype('category') # For repeated strings
Problem: Slow DataFrame operations
# Debug: Profile your code
%timeit df.apply(func) # Compare with vectorized
# Solution: Use vectorized operations
df['result'] = np.where(df['x'] > 0, df['x'] * 2, 0) # Instead of apply
Problem: Import errors
# Solution: Check environment
pip list | grep pandas
pip install --upgrade pandas numpy
# Virtual environment best practice
python -m venv venv
source venv/bin/activate # Linux/Mac
pip install -r requirements.txt
Problem: Data type mismatches
# Debug: Check types
print(df.dtypes)
# Solution: Convert types explicitly
df['date'] = pd.to_datetime(df['date'])
df['price'] = pd.to_numeric(df['price'], errors='coerce')
Debug Checklist
- Check Python and library versions
- Verify data types with
df.dtypes - Profile with
%timeitbefore optimizing - Use
df.info()for memory usage - Check for NaN values with
df.isna().sum()
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