> Minor nit: .pth semantics should be identical to site.py .pth
> semantics. I.e. lines that start with "import" should be exec'd.
Barry & I had an offline discussion about this.
Some conclusions:
- pth files for sys.path and pth-ish files for packages should
probably have different extensions; otherwise e.g. paths named in
zope.pth would be added both to sys.path and to zope.__path__, which
is a bad idea. I propose using pkg as the extension for package.s
- Nobody remembers why there is a special case in site.py for lines in
the .pth file that start with 'import', except that Martin von
Loewis once wanted this. I propose not to duplicate this
functionality in .pkg files.
- We need to look both for subdirectories and for .pkg files --
different styles of administering a system call for both approaches.
- We should only accept subdirectories that have an __init__.py.
- I'm punting for now on an extension to cope with finding things in
other importers.
Current draft, incorporating all these changes:
######################################################################
"""Utilities to support packages."""
import os
import sys
def extend_path(path, name):
"""Extend a package's path.
Intended use is to place the following code in a package's __init__.py:
from pkgutil import extend_path
__path__ = extend_path(__path__, __name__)
This will add to the package's __path__ all subdirectories of
directories on sys.path named after the package. This is useful
if one wants to distribute different parts of a single logical
package as multiple directories.
It also looks for *.pkg files beginning with __name__. This
feature is similar to *.pth files, except it doesn't special-case
lines starting with 'import'.
"""
pname = os.path.join(*name.split('.')) # Reconstitute as relative path
sname = os.extsep.join(name.split('.')) # Just in case os.extsep != '.'
sname_pkg = sname + os.extsep + "pkg"
init_py = "__init__" + os.extsep + "py"
path = path[:]
for dir in sys.path:
if isinstance(dir, (str, unicode)) and os.path.isdir(dir):
subdir = os.path.join(dir, pname)
# XXX This may still add duplicate entries to path on
# case-insensitive filesystems
initfile = os.path.join(subdir, init_py)
if subdir not in path and os.path.isfile(initfile):
path.append(subdir)
# XXX Is this the right thing for subpackages like
# zope.app? It looks for a file named "zope.app.pkg"
pkgfile = os.path.join(dir, sname_pkg)
if os.path.isfile(pkgfile):
try:
f = open(pkgfile)
except IOError, msg:
sys.stderr.write("Can't open %s: %s\n" %
(pkgfile, msg))
else:
for line in f:
line = line.rstrip('\n')
if not line or line.startswith('#'):
continue
path.append(line) # Don't check for existence!
f.close()
return path
######################################################################
--Guido van Rossum (home page: http://www.python.org/~guido/)
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