Re: Hey, get this! [was: import from database]

Steve Holden Wed, 02 Feb 2005 06:45:04 -0800

Steve Holden wrote:

Peter Otten wrote:
Steve Holden wrote:
This is even stranger: it makes it if I import the module a second time:
[second import seems to succeed]
Maybe you are experiencing some version confusion? What you describe looks much like the normal Python 2.3 behaviour (with no import hook involved) whereas you seem to operate on the 2.4 library. A partially initialized module object is left behind in sys.modules and seen by further import attempts.
I agree that this is 2.3-like behavior, but Python cannot lie ...
[EMAIL PROTECTED] ~/Projects/Python/dbimp
$ python
Python 2.4 (#1, Dec  4 2004, 20:10:33)
[GCC 3.3.3 (cygwin special)] on cygwin
Type "help", "copyright", "credits" or "license" for more information.
 >>>

Just to make things simpler, and (;-) to appeal to a wider audience, here is a program that doesn't use database at all (it loads the entire standard library into a dict) and still shows the error.

What *I* would like to know is: who is allowing the import of bsddb.os, thereby somehow causing the code of the os library module to be run a second time.

#
# Establish standard library in dict
#
import os
import glob
import sys
import marshal
import new

def importpy(dct, path, modname, package):
    c = compile(file(path).read(), path, "exec")
    dct[modname] = (marshal.dumps(c), package, path)
    if package:
        print "Package", modname, path
    else:
        print "Module", modname, path

def importall(dct, path, modlist): os.chdir(path) for f in glob.glob("*"): if os.path.isdir(f): fn = os.path.join(path, f, "__init__.py") if os.path.exists(fn): ml = modlist + [f] importpy(dct, fn, ".".join(ml), 1) importall(dct, os.path.join(path, f), ml) elif f.endswith('.py') and '.' not in f[:-3] and f != "__init__.py": importpy(dct, os.path.join(path, f), ".".join(modlist+[f[:-3]]), 0)

class dbimporter(object):

    def __init__(self, item, *args, **kw):
        ##print "dbimporter: item:", item, "args:", args, "keywords:", kw
        if item != "*db*":
            raise ImportError
        print "Accepted", item

    def find_module(self, fullname, path=None):
        print "find_module:", fullname, "from", path
        if fullname not in impdict:
            #print "Bailed on", fullname
            return None
        else:
            print "found", fullname, "in db"
            return self

    def load_module(self, modname):
        print "load_module:", modname
        if modname in sys.modules:
            return sys.modules[modname]
        try:
            row = impdict[modname]
        except KeyError:
            #print modname, "not found in db"
            raise ImportError, "DB module %s not found in modules"
        code, package, path = row
        code = marshal.loads(code)
        module = new.module(modname)
        sys.modules[modname] = module
        module.__name__ = modname
        module.__file__ = path # "db:%s" % modname
        module.__loader__ = dbimporter
        if package:
            module.__path__ = sys.path
        exec code in module.__dict__
        print modname, "loaded:", repr(module), "pkg:", package
        return module

def install(): sys.path_hooks.append(dbimporter) sys.path_importer_cache.clear() # probably not necessary sys.path.insert(0, "*db*") # probably not needed with a metea-path hook?

if __name__ == "__main__":
    impdict = {}
    for path in sys.argv[1:]:
        importall(impdict, path, [])
    install()
    import bsddb

Running this against a copy of the Python 2.4 standard library in C:\Lib gives me

[...] Module _strptime C:\Lib\_strptime.py Module _threading_local C:\Lib\_threading_local.py Module __future__ C:\Lib\__future__.py Accepted *db* find_module: bsddb from None found bsddb in db load_module: bsddb find_module: bsddb._bsddb from None find_module: bsddb.sys from None find_module: bsddb.os from None find_module: bsddb.nt from None find_module: bsddb.ntpath from None find_module: bsddb.stat from None Traceback (most recent call last): File "C:\Steve\Projects\Python\dbimp\dictload.py", line 79, in ? import bsddb File "C:\Steve\Projects\Python\dbimp\dictload.py", line 65, in load_module exec code in module.__dict__ File "C:\Lib\bsddb\__init__.py", line 62, in ? import sys, os File "C:\Python24\lib\os.py", line 133, in ? from os.path import (curdir, pardir, sep, pathsep, defpath, extsep, altsep, ImportError: No module named path

The 2.3 bsddb library doesn't cause the same problems (and even loads into 2.4 quite nicely). Lots of modules *will* import, and most packages don't seem to cause problems. Anyone give me a pointer here?

regards
 Steve
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Steve Holden                           http://www.holdenweb.com/
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Re: Hey, get this! [was: import from database]

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