Importing modules through directory shortcuts on Windows

[Brian Quinlan]

Recently, I became responsible for maintaining some Python code, which
was organized as follows:

user/pylib
ui
...
project2/pylib
ui
...
project3/pylib
ui
...
python-packages/user => /user/pylib
project2 => /project2/pylib
project3 => /project3/pylib

The idea is that "python-packages" is added to sys.path and then every
project can import the library package from every other project. NOTE: I
think that this structure is crazy but I'm just the poor maintenance
programmer.

Anyway, the problem is that Windows does not have a symlink facility to
accommodate this (AFAIK) and the Python import mechanism does not
resolve shortcuts.

Therefore, I wrote a very simple import hook to get around that problem.
If you are interested, the code is here:
http://www.sweetapp.com/shortcut/shortcutimporter.py

BTW, does anyone else think that this functionality should be part of
core Python?

Cheers,
Brian

[Thomas Heller]

I wonder (but haven't yet figured out) if something similar can be achived
with pkgutil and one or more .pkg files.

Thomas

[Duncan Booth]

Brian Quinlan wrote:

> Anyway, the problem is that Windows does not have a symlink facility to
> accommodate this (AFAIK) and the Python import mechanism does not
> resolve shortcuts.

Windows does have the equivalent of symlinks provided you are running on
NTFS with Windows 2000 or later (Google for 'XP junction'). However, by
default the system provides no support for manipulating junction points, so
they are only really useful in an environment where you can control the
tools on the system, not something you can expect to use on arbitrary
systems.

[Roger Upole]

You can use win32file.DeviceIoControl to link directories.
I can post some code to do so if anyone's interested.

Roger

"Brian Quinlan" <br...@sweetapp.com> wrote in message news:mailman.5014.1146058...@python.org...

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[Tim Golden]

[Roger Upole]

| You can use win32file.DeviceIoControl to link directories.
| I can post some code to do so if anyone's interested.

I'd certainly be interested...

Thanks
TJG

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[Roger Upole]

Warning: Ugly code ahead

import win32con, winioctlcon, winnt
import win32file, win32api
import os, struct

temp_dir=win32api.GetTempPath()
temp1=win32api.GetTempFileName(temp_dir,'rpp')[0]
win32file.DeleteFile(temp1)
os.mkdir(temp1)
temp2=win32api.GetTempFileName(temp_dir,'rpp')[0]
win32file.DeleteFile(temp2)
os.mkdir(temp2)
print temp1, temp2

temp2_abs=u'\\??\\'+temp2
printname=unicode(os.path.split(temp2)[1])
temp2buf=buffer(temp2_abs)[:]
printnamebuf=buffer(printname)[:]

## ???? need figure out how print name should be placed in the buffer, think it needs to follow an
## explicit double null terminator after the target string
printnamebuf=''

databufsize=len(temp2buf)+len(printnamebuf) ## final size includes everything past the reparse tag
fmt="LHHHHHH%ss" %(databufsize+4)
buf=struct.pack(fmt, winnt.IO_REPARSE_TAG_MOUNT_POINT,
databufsize+12, 0, 0, len(temp2buf), len(temp2buf)+2,
len(printnamebuf), temp2buf+printnamebuf+'\0\0\0\0')
bufsize=struct.calcsize(fmt)

h = win32file.CreateFile(temp1, win32con.GENERIC_READ|win32con.GENERIC_WRITE,
win32con.FILE_SHARE_READ|win32con.FILE_SHARE_WRITE|win32con.FILE_SHARE_DELETE, None,
win32con.OPEN_EXISTING, win32file.FILE_FLAG_BACKUP_SEMANTICS|win32file.FILE_FLAG_OPEN_REPARSE_POINT, 0)

## old_buf=win32file.DeviceIoControl(h, winioctlcon.FSCTL_GET_REPARSE_POINT,'',winnt.MAXIMUM_REPARSE_DATA_BUFFER_SIZE,None)
win32file.DeviceIoControl(h, winioctlcon.FSCTL_SET_REPARSE_POINT, buf, 0, None)

## create a subdir in redirected dir and make sure it shows up in target dir
os.mkdir(os.path.join(temp1,'new_dir'))
assert os.path.isdir(os.path.join(temp2,'new_dir'))
h.Close()

Roger

"Tim Golden" <tim.g...@viacom-outdoor.co.uk> wrote in message news:mailman.5039.1146126...@python.org...

[Tim Golden]

[Roger Upole]

| [... snipped ugly code ...]

Thanks; I'll have to find the time to experiment
with that a bit.