Loading......

Password

Python Libraries and Modules

Core Concepts

• Module: A single .py file containing Python code
• Package: A folder containing multiple modules (requires __init__.py)
• Library: A collection focusing on functionality, may include multiple packages and modules
• Standard Library: Pre-installed modules that come with Python, always available
• Third-Party Libraries: External packages available for download from PyPI (Python Package Index)

Import Methods

Three primary ways to import libraries:

1. Full Import: Import the entire module
   • Syntax: import module_name
   • Usage: module_name.function()
   • Prevents name conflicts
2. Specific Import: Import specific functions or classes
   • Syntax: from module_name import function_name
   • Usage: function_name() directly
   • Makes code cleaner
3. Alias Import: Import with a shortened name
   • Syntax: import module_name as alias
   • Usage: alias.function()
   • Saves typing for long module names
4. Combined Approach: Import specific with alias
   • Syntax: from module_name import function as alias

Python’s Built-in Help

• Discover all available standard libraries: help('modules')
• Official documentation: docs.python.org/3/library

pip - Python Package Manager

• Built-in tool for package management (available in Python 3.4+)
• Main commands:
  • pip3 install package_name
  • pip3 uninstall package_name
  • pip3 list (shows installed packages with versions)
  • pip3 install --upgrade package_name
  • pip3 install package_name==version
• Check version: pip3 --version

Using Mirrors for Faster Downloads

• Temporary mirror: pip3 install -i https://pypi.tuna.tsinghua.edu.cn/simple package_name
• Permanent configuration: pip3 config set global.index-url https://pypi.tuna.tsinghua.edu.cn/simple
• Creates configuration file at ~/.config/pip/pip.conf

Key Standard Library Modules

math Module

• Mathematical functions and constants
• Key attributes: math.pi, math.sqrt(), math.pow()

datetime Module

• Date and time handling
• datetime.datetime.now(): Returns current local time (year, month, day, hour, minute, second, microsecond)
• datetime.timedelta(): Represents time intervals for calculations
  • Parameters: days, hours, minutes
• Formatting: strftime("%H:%M") creates custom time strings

random Module

• Random number generation
• random.choice(sequence): Selects random element
• random.randint(a, b): Returns random integer between a and b (inclusive)

os Module

• Operating system interface for path and directory operations
• os.path.exists(path): Checks if path exists
• os.makedirs(path): Creates directory (including parent directories)
• os.listdir(folder): Lists all files in directory
• os.path.join(path, file): Safely joins path components

shutil Module

• High-level file operations
• shutil.copy2(src, dst): Copies file while preserving metadata

Third-Party Libraries: requests

• HTTP library for web communication
• Basic usage pattern:

  response = requests.get("URL")
  response.status_code  # HTTP status code
  response.text  # Response content as string
  

• Supports query parameters via f-strings: f"http://wttr.in/{city}?format=3"

Practical Patterns

Combining Multiple Modules

• Import and use different modules in a single script
• Common combination: datetime for timestamps with requests for data fetching

Timezone Considerations

• datetime.datetime.now() returns local system time
• Applications requiring consistent timestamps must handle timezone awareness explicitly

File Operations Workflow

1. Verify paths with os.path.exists()
2. Create directories with os.makedirs() if needed
3. List files using os.listdir()
4. Perform operations with shutil.copy2() or similar functions