I’m working with a Python script that utilizes pybind11 and includes a function to install a package within a virtual environment. The function, install_package, looks like this:

def install_package(self, package_path, venv_dir):
    """
    Installs a Python package from the given path into a virtual environment.

    Args:
        package_path (str): The path to the directory containing the package to install.
        venv_dir (str): The directory path of the virtual environment.
    """

    # Construct the pip command with flags
    command = ["pip", "install", "--target", venv_dir, "--use-feature=in-tree-build", "--upgrade", "--no-clean", package_path]

    try:
        # Execute the pip command in a subprocess
        subprocess.run(command, check=True)
        print(f"Package successfully installed into virtual environment: {venv_dir}")
    except subprocess.CalledProcessError as error:
        print(f"Error installing package: {error}")

This function works perfectly when executed directly from a shell script. However, when I call it from within my Python script, I encounter a PermissionError. Here’s the complete error message:

Using legacy 'setup.py install' for controller-module, since package 'wheel' is not installed.
Installing collected packages: controller-module
    Running setup.py install for controller-module: started
    Running setup.py install for controller-module: finished with status 'done'
Successfully installed controller-module-3.0.0
ERROR: Exception:
Traceback (most recent call last):
  File "C:Usersproject_pathvenvlibsite-packagespip_internalclibase_command.py", line 173, in _main
    status = self.run(options, args)
  File "C:Usersproject_pathvenvlibsite-packagespip_internalclireq_command.py", line 203, in wrapper
    return func(self, options, args)
  File "C:Usersproject_pathvenvlibsite-packagespip_internalcommandsinstall.py", line 446, in run
    self._handle_target_dir(
  File "C:Usersproject_pathvenvlibsite-packagespip_internalcommandsinstall.py", line 503, in _handle_target_dir
    os.remove(target_item_dir)
PermissionError: [WinError 5] Access denied: 'C:\project_path\venv\Lib\site-packages\controller_module.cp310-win_amd64.pyd'

Environment:
Python version (e.g., 3.10)
Operating System (Windows 11)

Why does the install_package function exhibit this permission error only when called from a Python script, and how can I resolve it to ensure successful installation within the script itself?