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Re: Understanding .pth in site-packages

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Subject Re: Understanding .pth in site-packages
From Philip Semanchuk <philip@semanchuk.com>
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Date Sat, 27 Aug 2011 23:01:11 -0400
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On Aug 27, 2011, at 6:49 PM, Josh English wrote:

> When I run: os.listdir('c:\Python27\lib\site-packages') I get the contents in order, so the folders come before .pth files (as nothing comes before something.)

That's one definition of "in order". =)


> I would guess Python is using os.listdir. Why wouldn't it?

If you mean that Python uses os.listdir() during import resolution, then yes I agree that's probable. And os.listdir() doesn't guarantee any consistent order. In fact, the documentation explicitly states that the list is returned in arbitrary order. Like a lot of things in Python, os.listdir() probably relies on the underlying C library which varies from system to system. (Case in point -- on my Mac, os.listdir() returns things in the same order as the 'ls' command, which is case-sensitive alphabetical, files & directories mixed -- different from Windows.)

So if import relies on os.listdir(), then you're relying on arbitrary resolution when you have a .pth file that shadows a site-packages directory. Those rules will probably work consistently on your particular system, you're developing a habit around what is essentially an implementation quirk.  

Cheers
Philip

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Thread

Understanding .pth in site-packages Josh English <Joshua.R.English@gmail.com> - 2011-08-27 09:56 -0700
  Re: Understanding .pth in site-packages Philip Semanchuk <philip@semanchuk.com> - 2011-08-27 13:18 -0400
    Re: Understanding .pth in site-packages Josh English <Joshua.R.English@gmail.com> - 2011-08-27 10:57 -0700
      Re: Understanding .pth in site-packages "OKB (not okblacke)" <brenNOSPAMbarn@NObrenSPAMbarn.net> - 2011-08-27 19:45 +0000
        Re: Understanding .pth in site-packages Josh English <Joshua.R.English@gmail.com> - 2011-08-27 15:39 -0700
          Re: Understanding .pth in site-packages "OKB (not okblacke)" <brenNOSPAMbarn@NObrenSPAMbarn.net> - 2011-08-28 05:20 +0000
    Re: Understanding .pth in site-packages Josh English <Joshua.R.English@gmail.com> - 2011-08-27 10:57 -0700
      Re: Understanding .pth in site-packages Philip Semanchuk <philip@semanchuk.com> - 2011-08-27 14:07 -0400
      Re: Understanding .pth in site-packages Terry Reedy <tjreedy@udel.edu> - 2011-08-27 16:14 -0400
      Re: Understanding .pth in site-packages Philip Semanchuk <philip@semanchuk.com> - 2011-08-27 16:28 -0400
        Re: Understanding .pth in site-packages Josh English <Joshua.R.English@gmail.com> - 2011-08-27 15:49 -0700
        Re: Understanding .pth in site-packages Josh English <Joshua.R.English@gmail.com> - 2011-08-27 15:49 -0700
          Re: Understanding .pth in site-packages Philip Semanchuk <philip@semanchuk.com> - 2011-08-27 23:01 -0400
      Re: Understanding .pth in site-packages Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2011-08-27 13:53 -0700
        Re: Understanding .pth in site-packages Josh English <Joshua.R.English@gmail.com> - 2011-08-27 15:41 -0700
        Re: Understanding .pth in site-packages Josh English <Joshua.R.English@gmail.com> - 2011-08-27 15:41 -0700
          Re: Understanding .pth in site-packages Stephen Hansen <me+list/python@ixokai.io> - 2011-08-27 16:44 -0700
  Re: Understanding .pth in site-packages Peter Otten <__peter__@web.de> - 2011-08-27 19:29 +0200
  Re: Understanding .pth in site-packages Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2011-08-27 13:53 -0700

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