python3: write sitecustomize.py in formula.

1 files changed, 54 insertions, 0 deletions

diff --git a/Library/Formula/python3.rb b/Library/Formula/python3.rb
index 1cc2ac045..5f7419c96 100644
--- a/Library/Formula/python3.rb
+++ b/Library/Formula/python3.rb
@@ -130,6 +130,10 @@ class Python3 < Formula
     # Symlink the prefix site-packages into the cellar.
     ln_s site_packages, site_packages_cellar
 
+    # Write our sitecustomize.py
+    Dir["#{site_packages}/*.py{,c,o}"].each {|f| Pathname.new(f).unlink }
+    (site_packages/"sitecustomize.py").write(sitecustomize)
+
     # "python3" executable is forgotten for framework builds.
     # Make sure homebrew symlinks it to HOMEBREW_PREFIX/bin.
     ln_s "#{bin}/python#{VER}", "#{bin}/python3" unless (bin/"python3").exist?
@@ -217,6 +221,56 @@ class Python3 < Formula
     end
   end
 
+  def sitecustomize
+    <<-EOF.undent
+      # This file is created by Homebrew and is executed on each python startup.
+      # Don't print from here, or else python command line scripts may fail!
+      # <https://github.com/Homebrew/homebrew/wiki/Homebrew-and-Python>
+      import os
+      import sys
+
+      if sys.version_info[0] != 3:
+          # This can only happen if the user has set the PYTHONPATH for 3.x and run Python 2.x or vice versa.
+          # Every Python looks at the PYTHONPATH variable and we can't fix it here in sitecustomize.py,
+          # because the PYTHONPATH is evaluated after the sitecustomize.py. Many modules (e.g. PyQt4) are
+          # built only for a specific version of Python and will fail with cryptic error messages.
+          # In the end this means: Don't set the PYTHONPATH permanently if you use different Python versions.
+          exit('Your PYTHONPATH points to a site-packages dir for Python 3.x but you are running Python ' +
+               str(sys.version_info[0]) + '.x!\\n     PYTHONPATH is currently: "' + str(os.environ['PYTHONPATH']) + '"\\n' +
+               '     You should `unset PYTHONPATH` to fix this.')
+      else:
+          # Only do this for a brewed python:
+          opt_executable = '#{HOMEBREW_PREFIX}/opt/python3/bin/python#{VER}'
+          if os.path.realpath(sys.executable) == os.path.realpath(opt_executable):
+              # Remove /System site-packages, and the Cellar site-packages
+              # which we moved to lib/pythonX.Y/site-packages. Further, remove
+              # HOMEBREW_PREFIX/lib/python because we later addsitedir(...).
+              sys.path = [ p for p in sys.path
+                           if (not p.startswith('/System') and
+                               not p.startswith('#{HOMEBREW_PREFIX}/lib/python') and
+                               not (p.startswith('#{HOMEBREW_PREFIX}/Cellar/python') and p.endswith('site-packages'))) ]
+
+              # LINKFORSHARED (and python-config --ldflags) return the
+              # full path to the lib (yes, "Python" is actually the lib, not a
+              # dir) so that third-party software does not need to add the
+              # -F/#{HOMEBREW_PREFIX}/Frameworks switch.
+              # Assume Framework style build (default since months in brew)
+              try:
+                  from _sysconfigdata import build_time_vars
+                  build_time_vars['LINKFORSHARED'] = '-u _PyMac_Error #{HOMEBREW_PREFIX}/opt/python3/Frameworks/Python.framework/Versions/#{VER}/Python'
+              except:
+                  pass  # remember: don't print here. Better to fail silently.
+
+              # Set the sys.executable to use the opt_prefix
+              sys.executable = opt_executable
+
+          # Tell about homebrew's site-packages location.
+          # This is needed for Python to parse *.pth.
+          import site
+          site.addsitedir('#{HOMEBREW_PREFIX}/lib/python#{VER}/site-packages')
+    EOF
+  end
+
   def caveats
     text = <<-EOS.undent
       Setuptools and Pip have been installed. To update them