New site.py semantics. Searches in

<*prefix>/lib/python<version>/packages for *.pth files containing
directories that are appended to sys.path.

Lib/site.py

@@ -1,47 +1,122 @@
-"""Hook to allow easy access to site-specific modules.
+"""Append module search paths for third-party packages to sys.path.
 
-Scripts or modules that need to use site-specific modules should place
+****************************************************************
+* This module is automatically imported during initialization. *
+****************************************************************
 
-	import site
+In earlier versions of Python (up to 1.5a3), scripts or modules that
+needed to use site-specific modules would place ``import site''
+somewhere near the top of their code.  Because of the automatic
+import, this is no longer necessary (but code that does it still
+works).
 
-somewhere near the top of their code.  This will append up to two
-site-specific paths ($prefix/lib/site-python and
-$exec_prefix/lib/site-python) to the module search path.  ($prefix
-and $exec_prefix are configuration parameters, and both default
-to /usr/local; they are accessible in Python as sys.prefix and
-sys.exec_prefix).
+This will append site-specific paths to to the module search path.  It
+starts with sys.prefix and sys.exec_prefix (if different) and appends
+lib/python<version>/packages.  The resulting directory, if it exists,
+is added to sys.path, and also inspected for path configuration files.
 
-Because of Python's import semantics, it is okay for more than one
-module to import site -- only the first one will execute the site
-customizations.  The directories are only appended to the path if they
-exist and are not already on it.
+A path configuration file is a file whose name has the form
+<package>.pth; its contents are additional directories (one per line)
+to be added to sys.path.  Non-existing directories (or
+non-directories) are never added to sys.path; no directory is added to
+sys.path more than once.  Blank lines and lines beginning with
+\code{#} are skipped.
 
-Sites that wish to provide site-specific modules should place them in
-one of the site specific directories; $prefix/lib/site-python is for
-Python source code and $exec_prefix/lib/site-python is for dynamically
-loadable extension modules (shared libraries).
+For example, suppose sys.prefix and sys.exec_prefix are set to
+/usr/local and there is a directory /usr/local/python1.5/packages with
+three subdirectories, foo, bar and spam, and two path configuration
+files, foo.pth and bar.pth.  Assume foo.pth contains the following:
+
+  # foo package configuration
+  foo
+  bar
+  bletch
+
+and bar.pth contains:
+
+  # bar package configuration
+  bar
+
+Then the following directories are added to sys.path, in this order:
+
+  /usr/local/lib/python1.5/packages/bar
+  /usr/local/lib/python1.5/packages/foo
+
+Note that bletch is omitted because it doesn't exist; bar precedes foo
+because bar.pth comes alphabetically before foo.pth; and spam is
+omitted because it is not mentioned in either path configuration file.
 
 After these path manipulations, an attempt is made to import a module
-named sitecustomize, which can perform arbitrary site-specific
-customizations.  If this import fails with an ImportError exception,
-it is ignored.
+named sitecustomize, which can perform arbitrary additional
+site-specific customizations.  If this import fails with an
+ImportError exception, it is silently ignored.
 
-Note that for non-Unix systems, sys.prefix and sys.exec_prefix are
-empty, and the path manipulations are skipped; however the import of
-sitecustomize is still attempted.
+Note that for some non-Unix systems, sys.prefix and sys.exec_prefix
+are empty, and then the path manipulations are skipped; however the
+import of sitecustomize is still attempted.
 
-XXX Any suggestions as to how to handle this for non-Unix systems???
 """
 
+print "loading site.py"
+
 import sys, os
 
-for prefix in sys.prefix, sys.exec_prefix:
-    if prefix:
-	sitedir = os.path.join(prefix, os.path.join("lib", "site-python"))
-	if sitedir not in sys.path and os.path.isdir(sitedir):
+def addsitedir(sitedir):
+    if sitedir not in sys.path:
 	sys.path.append(sitedir)	# Add path component
+    try:
+	names = os.listdir(sitedir)
+    except os.error:
+	return
+    names = map(os.path.normcase, names)
+    names.sort()
+    for name in names:
+	if name[-4:] == ".pth":
+	    addpackage(sitedir, name)
+
+def addpackage(sitedir, name):
+    fullname = os.path.join(sitedir, name)
+    try:
+	f = open(fullname)
+    except IOError:
+	return
+    while 1:
+	dir = f.readline()
+	if not dir:
+	    break
+	if dir[0] == '#':
+	    continue
+	if dir[-1] == '\n':
+	    dir = dir[:-1]
+	dir = os.path.join(sitedir, dir)
+	if dir not in sys.path and os.path.exists(dir):
+	    sys.path.append(dir)
+
+prefixes = [sys.prefix]
+if sys.exec_prefix != sys.prefix:
+    prefixes.append(sys.exec_prefix)
+for prefix in prefixes:
+    if prefix:
+	if sys.platform[:3] in ('win', 'mac'):
+	    sitedir = prefix
+	else:
+	    sitedir = os.path.join(prefix,
+				   "lib",
+				   "python" + sys.version[:3],
+				   "packages")
+	if os.path.isdir(sitedir):
+	    addsitedir(sitedir)
 
 try:
     import sitecustomize		# Run arbitrary site specific code
 except ImportError:
     pass				# No site customization module
+
+def _test():
+    print "sys.path = ["
+    for dir in sys.path:
+	print "    %s," % `dir`
+    print "]"
+
+if __name__ == '__main__':
+    _test()