Learning Code Screenshot

Objectives

Automatically generate both code and output screenshots from Python scripts for inclusion in assignment documentation.

Instructions

1. Two Types of Screenshots

Code Screenshots:

• •Extract code sections from .py file
• •Show the actual Python code
• •Light background with syntax highlighting

Output Screenshots:

• •Capture console output during execution
• •Show results, prints, data displays
• •Clean monospace formatting

2. Identify Code Sections

Parse Python script to identify:

• •Step markers (comments like # Step 1:, # Step 2:)
• •Function definitions
• •Major code blocks
• •Section separators

3. Capture Output

During script execution:

• •Redirect stdout to buffer
• •Capture print statements
• •Save output as image
• •Match with corresponding code section

4. Generate Screenshots

Code screenshots:

• •Use monospace font
• •Light background (#f8f8f8)
• •Tight margins
• •Name: step01_xxx_code.png

Output screenshots:

• •Use monospace font
• •White or light background
• •Show actual execution results
• •Name: step01_xxx.png (without _code suffix)

5. Naming Convention

images/
├── step01_load_data_code.png      # Code
├── step01_load_data.png           # Output
├── step02_print_stats_code.png    # Code
├── step02_print_stats.png         # Output
└── ...

Implementation Approaches

Approach 1: Integrated Logging (Recommended)

Add a Logger class to the main script to automatically save all terminal output to output.txt while still displaying it in the console:

import sys
import os

class Logger(object):
    def __init__(self, filename):
        self.terminal = sys.stdout
        self.log = open(filename, "w", encoding="utf-8")

    def write(self, message):
        self.terminal.write(message)
        self.log.write(message)

    def flush(self):
        self.terminal.flush()
        self.log.flush()

# Usage:
os.makedirs('images', exist_ok=True)
sys.stdout = Logger('images/output.txt')

Approach 2: Separate Screenshot Generator

Run these scripts after your main code is finished. They parse the .py file for step markers and the captured output for corresponding sections.

# Generate code images
python generate_code_screenshots.py lab1_pca.py images/

# Generate result images (auto-includes step headers/separators)
python generate_output_screenshots.py lab1_pca.py images/

For detailed implementations: See references/screenshot-script.md

Usage Workflow

Option A: Automatic Logger (Recommended)

1. •Write Python script with:
   • •Step markers in comments (e.g., # Step 1:)
   • •Logger class integrated to auto-save output.txt
2. •Run script once:
   bash

   uv run python lab[n]_*.py
   

3. •Verify the generated lab[n]_images/output.txt looks professional.
4. •Run screenshot scripts to batch generate all images.

Option B: Manual Redirect

1. •Run script and manually save output to file:
   bash

   uv run python lab[n]_*.py > lab[n]_images/output.txt 2>&1
   

2. •Check output file - verify content (labels, spacing, labels conversion) is correct.
3. •Generate screenshots using the helper scripts:
   bash

   # Code screenshots
   uv run python generate_code_screenshots.py lab[n]_*.py lab[n]_images/
   # Result screenshots (maintains step header formatting)
   uv run python generate_output_screenshots.py lab[n]_*.py lab[n]_images/
   

Validation

Check generated screenshots:

• • All steps have code screenshots
• • All steps have output screenshots
• • Code is readable (font size appropriate)
• • Output is complete and formatted
• • No excessive whitespace
• • Filenames match template requirements
• • Images saved in correct directory

Common Patterns

Pattern 1: Lab with numbered steps

• •Code: step01_xxx_code.png
• •Output: step01_xxx.png

Pattern 2: Visualization steps

• •Code: step13_2d_plot_code.png
• •Output: step13_2d_plot.png (text output)
• •Visualization: lab1_pca_2d.png (actual plot)

Pattern 3: Comparison steps

• •Code: step11_comparison_code.png
• •Output: step11_comparison.png (shows both results)

Anti-Patterns

• •❌ Only capturing code without output
• •❌ Only capturing output without code
• •❌ Mismatched naming between code and output
• •❌ Screenshots with tiny font (unreadable)
• •❌ Excessive whitespace (wastes space)
• •❌ Missing step markers (can't identify sections)

For detailed examples: See references/screenshot-examples.md