Environment Creation

def create_environment(
    home_dir,
    site_packages=False,
    clear=False,
    prompt=None,
    search_dirs=None,
    download=False,
    no_setuptools=False,
    no_pip=False,
    no_wheel=False,
    symlink=True
):
    """
    Creates a new environment in home_dir.
    
    If site_packages is true, then the global site-packages/ directory
    will be on the path. If clear is true (default False) then the 
    environment will first be cleared.
    
    Parameters:
    - home_dir (str): Target directory for the virtual environment
    - site_packages (bool): Include global site-packages in environment path
    - clear (bool): Clear existing environment before creating new one
    - prompt (str): Custom prompt prefix for the environment
    - search_dirs (list): Directories to search for wheel packages
    - download (bool): Download packages if not found locally
    - no_setuptools (bool): Skip installing setuptools package
    - no_pip (bool): Skip installing pip package manager
    - no_wheel (bool): Skip installing wheel package
    - symlink (bool): Use symlinks instead of copying files when possible
    
    Returns:
    None
    
    Raises:
    OSError: If directory creation fails
    subprocess.CalledProcessError: If package installation fails
    """

import virtualenv

# Create basic environment
virtualenv.create_environment('/path/to/myenv')

# Create environment with global packages accessible
virtualenv.create_environment('/path/to/myenv', site_packages=True)

# Create clean environment (removes existing first)
virtualenv.create_environment('/path/to/myenv', clear=True)

# Create environment without pip
virtualenv.create_environment('/path/to/myenv', no_pip=True)

# Create environment with custom prompt
virtualenv.create_environment('/path/to/myenv', prompt='myproject')

def main():
    """
    Command-line interface entry point for virtualenv.
    
    Parses command-line arguments using optparse and creates virtual
    environment based on provided options. Handles all CLI flags including
    verbose/quiet modes, Python interpreter selection, and environment
    configuration options.
    
    Command-line options include:
    - --python PYTHON_EXE: Specify Python interpreter
    - --clear: Clear existing environment
    - --system-site-packages: Give access to global site-packages
    - --always-copy: Always copy files rather than symlinking
    - --prompt PROMPT: Custom environment prompt
    - --no-setuptools: Don't install setuptools
    - --no-pip: Don't install pip
    - --no-wheel: Don't install wheel
    - -v/--verbose: Increase verbosity
    - -q/--quiet: Decrease verbosity
    
    Parameters:
    Uses sys.argv for argument parsing
    
    Returns:
    None (exits process with appropriate exit code)
    
    Raises:
    SystemExit: On argument parsing errors or environment creation failures
    """

import virtualenv
import sys

# Use with custom arguments
sys.argv = ['virtualenv', '--python=python3.8', '/path/to/myenv']
virtualenv.main()

# Use with current sys.argv
virtualenv.main()

def resolve_interpreter(exe):
    """
    Resolve Python interpreter path from executable name or path.
    
    Takes a Python executable name (like 'python3.8') or path and resolves
    it to an absolute path, validating that it's a working Python interpreter.
    Handles platform-specific executable extensions and search paths.
    
    Parameters:
    - exe (str): Python executable name or path (e.g., 'python3.8', '/usr/bin/python')
    
    Returns:
    str: Absolute path to resolved Python interpreter
    
    Raises:
    RuntimeError: If interpreter cannot be found or is not executable
    """

import virtualenv

# Resolve system Python
python_path = virtualenv.resolve_interpreter('python')

# Resolve specific version
python38_path = virtualenv.resolve_interpreter('python3.8')

# Resolve from absolute path
custom_path = virtualenv.resolve_interpreter('/opt/python/bin/python')

def make_environment_relocatable(home_dir):
    """
    Make a virtual environment relocatable.
    
    Modifies the virtual environment to use relative paths instead of
    absolute paths, allowing the environment directory to be moved to
    different locations while maintaining functionality.
    
    Parameters:
    - home_dir (str): Path to virtual environment directory
    
    Returns:
    None
    
    Raises:
    OSError: If environment directory doesn't exist or modification fails
    """

import virtualenv

# Create environment then make it relocatable
virtualenv.create_environment('/path/to/myenv')
virtualenv.make_environment_relocatable('/path/to/myenv')

def find_wheels(projects, search_dirs):
    """
    Find wheel files for given projects.
    
    Searches specified directories for wheel files matching the given
    project names. Returns mapping of project names to wheel file paths.
    
    Parameters:
    - projects (list): List of project names to find wheels for
    - search_dirs (list): Directories to search for wheel files
    
    Returns:
    dict: Mapping of project names to wheel file paths
          Example: {'pip': '/path/to/pip-20.0.0-py2.py3-none-any.whl'}
    
    Raises:
    OSError: If search directories cannot be accessed
    """

import virtualenv

# Find wheels for specific projects
search_dirs = ['/path/to/wheels', '/another/wheel/dir']
wheels = virtualenv.find_wheels(['pip', 'setuptools'], search_dirs)
print(f"Found wheels: {wheels}")

def install_wheel(project_names, py_executable, search_dirs=None, download=False):
    """
    Install wheel packages in virtual environment.
    
    Installs specified packages using wheel format, searching in provided
    directories or downloading if needed. Commonly used for installing
    setuptools, pip, and wheel in new environments.
    
    Parameters:
    - project_names (list): List of package names to install
    - py_executable (str): Path to Python executable in target environment
    - search_dirs (list, optional): Directories to search for wheel files
    - download (bool): Download packages if not found locally
    
    Returns:
    None
    
    Raises:
    subprocess.CalledProcessError: If package installation fails
    """

import virtualenv

# Install default packages
python_exe = '/path/to/myenv/bin/python'
virtualenv.install_wheel(['pip', 'setuptools', 'wheel'], python_exe)

# Install with custom search directories
search_dirs = ['/path/to/wheels']
virtualenv.install_wheel(['mypackage'], python_exe, search_dirs=search_dirs)

# Install with download fallback
virtualenv.install_wheel(['requests'], python_exe, download=True)

def install_distutils(home_dir):
    """
    Install distutils configuration in virtual environment.
    
    Sets up distutils configuration files and paths for proper
    package installation behavior within the virtual environment.
    
    Parameters:
    - home_dir (str): Virtual environment home directory
    
    Returns:
    None
    
    Raises:
    OSError: If distutils configuration cannot be installed
    """

def install_activate(home_dir, bin_dir, prompt=None):
    """
    Install activation scripts in virtual environment.
    
    Creates platform-specific activation scripts (activate, activate.bat,
    activate.ps1, etc.) that set up environment variables for using
    the virtual environment.
    
    Parameters:
    - home_dir (str): Virtual environment home directory
    - bin_dir (str): Binary/scripts directory
    - prompt (str, optional): Custom prompt for activated environment
    
    Returns:
    None
    
    Raises:
    OSError: If activation scripts cannot be created
    """

def install_python_config(home_dir, bin_dir, prompt=None):
    """
    Install Python configuration script in virtual environment.
    
    Creates python-config script for querying Python configuration
    information within the virtual environment context.
    
    Parameters:
    - home_dir (str): Virtual environment home directory
    - bin_dir (str): Binary/scripts directory  
    - prompt (str, optional): Environment prompt
    
    Returns:
    None
    
    Raises:
    OSError: If python-config script cannot be created
    """

def install_python(home_dir, lib_dir, inc_dir, bin_dir, site_packages, clear, symlink=True):
    """
    Install Python interpreter and base environment.
    
    Core function that sets up the Python interpreter and standard library
    in the virtual environment. Handles copying/linking Python executable,
    standard library modules, and required system files.
    
    Parameters:
    - home_dir (str): Virtual environment home directory
    - lib_dir (str): Library directory path
    - inc_dir (str): Include directory path  
    - bin_dir (str): Binary/executable directory path
    - site_packages (bool): Whether to include system site-packages
    - clear (bool): Whether to clear existing installation
    - symlink (bool): Use symlinks when possible
    
    Returns:
    str: Path to installed Python executable
    
    Raises:
    OSError: If Python installation fails
    """

import virtualenv

# Install distutils after environment creation
virtualenv.install_distutils('/path/to/env')

# Install activation scripts
virtualenv.install_activate('/path/to/env', '/path/to/env/bin', prompt='myproject')

# Install python-config script
virtualenv.install_python_config('/path/to/env', '/path/to/env/bin')

# Install Python interpreter and base environment
home, lib, inc, bin = virtualenv.path_locations('/path/to/env')
python_exe = virtualenv.install_python(home, lib, inc, bin, site_packages=False, clear=False)
print(f"Python installed at: {python_exe}")

def get_installed_pythons():
    """
    Get mapping of available Python installations.
    
    Returns a dictionary mapping Python version strings to executable paths.
    On Windows, searches the registry for installed Python versions.
    On Unix systems, returns empty dict (relies on PATH search).
    
    Parameters:
    None
    
    Returns:
    dict: Mapping of version strings to executable paths
          Example: {'3.8': '/usr/bin/python3.8', '3.9': '/usr/bin/python3.9'}
    """

import virtualenv

# Get all available Python installations
pythons = virtualenv.get_installed_pythons()
print(f"Available Python versions: {list(pythons.keys())}")

# Use specific version if available
if '3.8' in pythons:
    virtualenv.create_environment('/path/to/myenv', python=pythons['3.8'])