Official documentation reads: "On Windows machines, the Python installation is usually placed in C:\Python35"

However, as of Python 3.5.0, usual installation directory on Windows is %LOCALAPPDATA%\Programs\Python.

Where does it go if the user hasn't set %LOCALAPPDATA% ?

Correct me if I am wrong, but as far as I know, %LOCALAPPDATA% is always set in Windows. When you want to install Python for just one user (which is the default), files are installed into this directory (LOCALAPPDATA). If you choose to install Python for all users, however, files are installed into %PROGRAMFILES% or %PROGRAMFILES(x86)%

I don't know the answer, but from the point of view of a webmaster who
gets support requests and doesn't have a windows system, it would be
very useful to already know where a person's python is supposed to
be, and thus good if the documentation said something along the
lines of:

If the user does not specify %LOCALAPPDATA% then it defaults to
<wherever that is> 

assuming there is such a default, of course.

Actually, under 'Using Python on Windows' at https://docs.python.org/3/using/windows.html, the documentation correctly refers to %LOCALAPPDATA% and %PROGRAMFILES% or %PROGRAMFILES(x86)% environment variables as the default installation directories for just-for-me installs and for all-user installs, respectively. The information provided in the tutorial part of the documentation (where it refers C:\Python35 as the default location) contradicts the one provided under 'Using Python on Windows'.

Here's a patch to try to modernize the whole section a bit, and to remove one of the two other instances of 'Python35' in the docs (the other instance is in the docs for pyvenv, which needs its own overhaul in a separate issue).

That patch looks good to me.

LOCALAPPDATA is set by the operating system, typically to C:\Users\<username>\AppData\Local (at least since Vista I think? Certainly since Win7). While it's possible to customize it, people who know how to do that won't be emailing webmasters expecting technical support.

Maybe that part of the tutorial should also include a link to https://docs.python.org/3/using/windows.html. This document contains all the details for using Python on Windows.

> LOCALAPPDATA is set by the operating system, typically to 
> C:\Users\<username>\AppData\Local (at least since Vista I
> think? Certainly since Win7

Vista introduced LOCALAPPDATA, so there's no problem referencing it in the docs for 3.5+. 

On a related note, section 3.4.4.1 [1] could be changed to use %LOCALAPPDATA% instead of referring to the shell function SHGetFolderPath and CSIDL_LOCAL_APPDATA. 

[1]: https://docs.python.org/3.5/using/windows.html#customization-via-ini-files

I'm closing this issue as out of date. The tutorial now refers to the py command and also the python3.9 command from the app distribution. The patch's addition of "followed by Enter" after "Control-Z" is still needed, but it's not related to this issue.