PyLogin - Streamlit Login System with Captcha

A user authentication system built with Streamlit, featuring image captcha verification, user registration, and login functionality.

Features

• Image Captcha: Randomly generates 4-character captchas with interference lines and dots for enhanced security
• User Registration: Supports new user registration with encrypted password storage
• User Login: Validates username, password, and captcha
• Session Management: Displays welcome page after login with logout functionality

Project Structure

pylogin/
 app.py              # Main Streamlit application
 captcha.py          # Captcha generation module
 user_manager.py     # User management module
 requirements.txt    # Project dependencies
©À users.json         # User data file (auto-generated)
 README.md          # This file

Installation

Prerequisites

• Python 3.7+
• pip package manager

Install Dependencies

pip install -r requirements.txt

Or install manually:

pip install streamlit Pillow

Run Application

streamlit run app.py

After starting, application will display access URLs:

Local URL: http://localhost:8501
Network URL: http://your-ip:8501

Usage

User Registration

1. Open your browser and navigate to application URL
2. Click on "Register" tab
3. Fill in registration information:
   • Username: Enter your desired username
   • Password: Enter your password (minimum 6 characters)
   • Confirm Password: Re-enter your password
   • Captcha: Enter captcha shown in image (case-insensitive)
4. Click "Register" button
5. Upon successful registration, a success message will appear. Click "Go to Login" to proceed

User Login

1. In "Login" tab, fill in your login information:
   • Username: Enter your username
   • Password: Enter your password
   • Captcha: Enter captcha shown in image (case-insensitive)
2. Click "Login" button
3. Upon successful login, a welcome page will be displayed

Refresh Captcha

• If captcha is unclear, click to "Refresh Captcha" button
• A new captcha will be generated; please enter to new captcha

Logout

• After logging in, click "Logout" button
• You will be redirected to login page

Important Notes

1. Captcha: Captcha is case-insensitive but must be entered accurately
2. Password Requirements: Password must be at least 6 characters long
3. Username: Usernames must be unique; duplicate usernames will result in an error
4. Data Storage: User data is stored in users.json file with SHA256 encrypted passwords
5. Session Management: Login state is maintained in browser sessions; page refresh does not lose login status

Technical Details

Captcha Generation

• Uses PIL (Pillow) library for image generation
• Randomly selects uppercase letters and numbers
• Adds interference lines and dots to prevent automated recognition
• Base64 encoded for embedding in web pages

User Management

• User data stored in JSON format
• Passwords encrypted using SHA256 hash algorithm
• Supports user registration and login validation

Streamlit Session

• Uses st.session_state for application state management
• Captcha, login status, and other information stored in session
• Prevents state loss on page refresh

FAQ

Q: Captcha always shows as incorrect?

A: Please ensure:

• Captcha is entered correctly (case-insensitive)
• Captcha has not expired (if inactive for a long time, please refresh)
• Not using an old captcha after multiple "Refresh Captcha" clicks

Q: Registration successful but cannot login?

A: Please check:

• Username and password are entered correctly
• Password case sensitivity
• Captcha is entered correctly

Q: How to delete a user?

A: You can directly edit users.json file to remove corresponding user entry, or clear entire file to reset all users.

Q: How to change password?

A: The current version does not support password modification. You need to delete user and re-register.

Development

Adding New Features

1. Add new pages or functionality in app.py
2. Add user management methods in user_manager.py
3. Modify captcha generation logic in captcha.py

Custom Configuration

You can modify to following configurations in app.py:

• Captcha length: Modify length parameter in CaptchaGenerator
• Captcha image size: Modify width and height parameters
• Minimum password length: Modify validation logic in registration form

License

This project is licensed under to Apache License 2.0 - see to LICENSE file for details.

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

Contact

For questions or suggestions, please contact to developer.