I have now sat next to three people installing Python on Windows, and all three hit the same wall: the installer finished, and typing python in the terminal did nothing useful. The installer isn't broken. There is one checkbox, and it is the entire story of this post.
Go to python.org, hover over Downloads, click Windows. You want the Windows installer (64-bit). If you're unsure which file you ended up with, the 64-bit installer's name ends in amd64.exe. Leave every install location at its default; the defaults are sensible. The site also points at the Microsoft Store — more on that trap below.
The very first installer screen has a checkbox at the bottom: Add python.exe to PATH. It ships unchecked. Tick it before you click Install Now.
PATH is the list of folders Windows searches when you type a command name. Without the checkbox, Windows has no idea where python.exe lives, so the command python simply doesn't exist as far as your terminal is concerned. With it, Python works from any folder, in any terminal. In my opinion the checkbox should ship ticked — until the installer agrees with me, tick it yourself. I have never once regretted it; I have spent two evenings undoing the decision not to.
Open Command Prompt — press Start, type cmd, press Enter — and run:
C:\Users\ada> python --version
Python 3.14.1Any version number starting with a 3 counts as success — the exact number doesn't matter yet.
If you see this instead, the checkbox didn't get ticked:
C:\Users\ada> python --version
'python' is not recognized as an internal or external command,
operable program or batch file.The fix that covers most cases: run the installer again, choose Modify, and tick the box this time. Meanwhile, the installer also adds a launcher called py, which works whether or not PATH is in a good mood:
C:\Users\ada> py --version
Python 3.14.1One more thing that bites people on a fresh machine: type python before installing anything and Windows opens the Microsoft Store, thanks to a little alias Microsoft ships with the system. Two consequences. First, don't install Python from the Store — the python.org installer is the one every tutorial and tool assumes you have. Second, if the Store page keeps opening even after a real install, the alias is shadowing the real Python: open Settings, search for app execution aliases (under Apps → Advanced app settings), and switch off the python.exe and python3.exe entries.
You can write Python in Notepad and run it from Command Prompt, and for the first ten minutes that is even instructive. After that you want an editor with a run button and error highlighting. VS Code is the free default — that's the next post. Other good editors exist; VS Code is simply the one most tutorials, including this site's, assume.