Windows FAQ¶

Answers to questions specifically concerning running, developing, and deploying Python on Microsoft Windows.

How do I make Python scripts run without typing `python`?¶

Windows uses file associations and the PATHEXT environment variable: 1. Ensure .PY is listed in your system PATHEXT variable (PATHEXT=.COM;.EXE;.BAT;.CMD;.PY). 2. The standard installer associates .py files with the Python Launcher (py.exe). 3. You can now execute scripts by name directly in PowerShell or Command Prompt:

.\myscript.py --flag

How do I create a standalone `.exe` from Python code?¶

To distribute your software to end-users who do not have Python installed, bundle your script, the Python runtime, and dependencies into an executable:

Using PyInstaller¶

# 1. Install PyInstaller
pip install pyinstaller

# 2. Bundle script into a single self-contained .exe file
pyinstaller --onefile --windowed main.py

The resulting dist/main.exe contains the Python interpreter, your bytecodes, and all dependencies in a single portable file.

What is a `*.pyd` file? Is it a DLL?¶

Yes! A .pyd file is simply a standard Windows Dynamic Link Library (.dll) with a different file extension.

CPython names C-extension modules with the .pyd extension to distinguish them from standard Windows DLLs. When you run import mymath, Python searches for mymath.pyd and calls its initialization entry point PyInit_mymath().

Reading and Writing the Windows Registry with `winreg`¶

The Python standard library includes the winreg module for interacting with the Windows Registry:

import winreg

# Read a registry key
key_path = r"Software\Microsoft\Windows\CurrentVersion"
try:
    with winreg.OpenKey(winreg.HKEY_LOCAL_MACHINE, key_path) as key:
        program_files_dir, _ = winreg.QueryValueEx(key, "ProgramFilesDir")
        print(f"Program Files Directory: {program_files_dir}")
except FileNotFoundError:
    print("Registry key not found")

Why does Python startup sometimes feel slow on Windows?¶

When Python imports a large package (like scipy or azure-sdk), it inspects and reads hundreds of small .py and .pyc files from disk.

On Windows, Windows Defender Real-Time Protection scans every file access. Adding your development directory or Python .venv folder to Windows Defender's Excluded Folders list can speed up Python startup and test execution by up to 300%.

Windows FAQ¶

How do I make Python scripts run without typing python?¶

How do I create a standalone .exe from Python code?¶