Failed to find real location of python.exe on a RAM disk

[nedman47]

Bug report

Bug description:

# Add a code block here, if required

Starting with 13.0 Python I get the warning "failed to find real location of python.exe" but only if I run it from a ram disk, never when i run it from a network share. I wrote an editor in Python back in 2017 and it was very fast except for startup, which took as long as 700 msec. I knew Microsoft C was fast in part because its DLLs were preloaded into memory. One day I was watching a Dave Plummer video on YouTube and he mentioned ram drives which I hadn't thought about since the days of MS-DOS. I found and installed IMDISK on Windows 10, and later Windows 11. The editor, and everything else, runs instantly and I've never had any problems with Python running from a ram disk. So, I'm writing to see if you guys could either make an exception for ram drives, or provide a way to turn off that warning message. Thanks in advance.

CPython versions tested on:

3.13

Operating systems tested on:

Windows

[zooba]

Hmm, if you're seeing that message, it must mean that we can't CreateFile or GetFinalPathNameByHandleW on your RAM disk. I've not come across that issue before - those are very common APIs that ought to work.

If you ignore the message on startup and do os.path.realpath(sys.executable) does it work? Or do you get a more specific error?

[ChrisDenton]

This is a very common failure mode for IMDISK. It doesn't integrate with the mount manager at all so it's impossible for GetFinalPathNameByHandleW to get the DOS drive letter.

The documentatiom even has a section on this which suggests getting the NT path then manually looking up the drive letter: https://learn.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-getfinalpathnamebyhandlew#remarks

Some third-party drivers can create a drive letter or mount point without using the Mount Manager. If the Mount Manager was not used to create the drive, then VOLUME_NAME_DOS or VOLUME_NAME_GUID will not succeed; only VOLUME_NAME_NT will be available. To determine the drive letter for the volume device path, use the QueryDosDevice function on every drive letter until a matching device name is found

[nedman47]

import os
import sys
print (os.path.realpath (sys.executable))

It printed "r:\python\python313\python.exe"

WMIC and PowerShell both see drive R:

Drive Snapshot is able to create and restore images as if it were a normal drive.

I've used IMDISK with Python 312, 311, and 310 for years with no apparent harm, and certainly no failure to locate messages. This is new with 313.

[ChrisDenton]

Try:

print (os.path.realpath (sys.executable, strict=True))

os.path.realpath has fallbacks for if GetFullPathNameW fails which can be disabled when setting strict to True.