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I tried to install python with make install DESTDIR=/home/blah 
./python -E ./setup.py install \ 
 --prefix=/ \ 
 --install-scripts=//bin \ 
 --install-platlib=//lib/python2.6/lib-dynload \ 
 --root=//home/blah 
running install 
running build 
running build_ext 
INFO: Can't locate Tcl/Tk libs and/or headers 
Failed to find the necessary bits to build these modules: 
_tkinter bsddb185 dl 
imageop sunaudiodev 
To find the necessary bits, look in setup.py in detect_modules() for 
the module's name. 
running build_scripts 
running install_lib 
creating /lib/python2.6 
error: could not create '/lib/python2.6': Permission denied 
make: *** [sharedinstall] Error 1 
I asked for help on the mailing list http://groups.google.com/group/comp.lang.python/browse_thread/thread/a0b0e49f7b8153d1#, and according to Martin v. Loewis 	
"If you have / as the prefix, you get two leading slashes, e.g. for 
//lib/python2.x. Any other prefix would have given you only a single 
slash: e.g. if it had been /usr, then you end up with /usr/lib/python2.x. 
Now, the code strips the first character to make it a relative path name 
(so that join can be used), which fails to work correctly if there are 
two leading slashes. "
I have attached the patch provided by him.

Thank you for the report. I’m not sure I understand the bug.
1) On my linux-based system, doing something on //dir is the same thing as /dir. Is this a cosmetic bug (IOW, you’d like to see /dir and not //dir)?
2) Since I’m not root, creating /lib/python2.6 fails, as it should. (Note that distutils only prints one slash, which is nice.) What is the bug?
3) It’s not clear in your past whether you ran with DESTDIR=/ or DESTDIR=/home/blah. Can you tell what you want to do and what is the bug?
Thanks again for the report.

I ran
./configure --prefix=/
make
make install DESTDIR=/home/blah 
The installation tries to install at /lib/python2.6 which fails because I am not root. It should not try to install anything at / because I specified DESTDIR as /home/blah.

Thanks for the clarification. Can you test the bug with the versions that are still open for bug fixes, that is 2.7, 3.1 and 3.2?
I’ll add tests and apply the original patch in distutils2. (distutils is frozen except for bug fixes, which this minor cosmetic change is not.)
I’m not a configure or make expert, so I’ll request help from other developers when we have more information.

Thanks for the reply Eric. It is not a cosmetic thing. It's a bug for sure in python-2.6 disutils. I will try out python-2.7, 3.1, 3.2 and update the bug.

I have no certitude, but a strong intuition that distutils is not guilty at all here, but the makefile is. When I talk about the cosmetic bug, I refer to the double slash thing.

See also issue1676135. Seems that the posters were wrong in concluding that the double slashes wouldn't bother anyone using prefix=/ :)

Re-adding distutils since we’re not sure the bug does not apply there.
aj, have you add time to test it?

Just ran into this bug myself with 3.2. Apparently this patch works: http://groups.google.com/group/comp.lang.python/msg/bd8818ab9d4af8d7 

Attached a patch that fixes it, only the line numbers have changed from Martin v. Loewis's patch. Used on 3.2.

Thanks. Have you run the test suite to make sure this doesn’t add bugs?

this is a very ugly bug and should be fixed ASAP
it's not only breaking python itself, but any package that uses this python installer, for example
http://seclists.org/nmap-dev/2012/q3/1025
what is preventing a merge of the existing patch ?

A unit test is needed.

Here's a patch to the problem. I refactored the code to work the same way on posix, nt, os2 environments. Plus a unit test for the posix environment that the bug was initially for.

Correction a typo error in the test.

George.Peristerakis' patch works
please apply

Can you please apply fix-root-prefix.patch? Or the updated version fof issue9674.patch that I've attached?
sysconfig tests will still fail and it will return bogus paths with double slash (e.g. //lib/python2.7) but at least Python will be installable with prefix=/ and will not mess up with files on root (/) when DESTDIR is set. That may not be complete solution but it's a step forward to that.

I have python (2.7.9 & 3.4.3) installed with prefix=/ which causes problems when change_root() doesn't lstrip() the path separators.
I have applied Ivailo's patch from 2015年02月13日 and handful of packages without issues.
Attached is a port of the patch to 3.4.3. Please note that the test failed (because it used the old distutils package, I suspect) and the win32 path handling is a bit messed up, but I don't have time to fix that ATM. It works as expected during runtime.

Issue 31114 is the same issue and proposes a workaround and another fix.

The problem is that the build system , Py_GetPath() and the distutils module do not handle correctly the case where the configure prefix is '/'.
Closing as a duplicate of issue 31114.