[Python-Dev] Why spawnvp not implemented on Windows? (original) (raw)

Alexey Borzenkov snaury at gmail.com
Fri Oct 13 02:46:23 CEST 2006

Forgot to include python-dev...

On 10/13/06, "Martin v. Löwis" <martin at v.loewis.de> wrote:

> Umm... do you mean that spawnp on python 2.5 is an absolute no? Yes. No new features can be added to Python 2.5.x; Python 2.5 has already been released.

Ugh... that's just not fair. Because of this there will be no spawnp in python for another two years. x_x

I have a workaround for this, that tweaks os module:

[...snip wrong code...]

It should have been:

if (not (hasattr(os, 'spawnvpe') or hasattr(os, 'spawnvp')) and hasattr(os, 'spawnve') and hasattr(os, 'spawnv')): def _os__spawnvpe(mode, file, args, env=None): import sys from errno import ENOENT, ENOTDIR from os import path, spawnve, spawnv, environ, defpath, pathsep, error

    if env is not None:
        func = spawnve
        argrest = (args, env)
    else:
        func = spawnv
        argrest = (args,)
        env = environ

    head, tail = path.split(file)
    if head:
        return func(mode, file, *argrest)
    if 'PATH' in env:
        envpath = env['PATH']
    else:
        envpath = defpath
    PATH = envpath.split(pathsep)
    if os.name == 'nt' or os.name == 'os2':
        PATH.insert(0, '')
    saved_exc = None
    saved_tb = None
    for dir in PATH:
        fullname = path.join(dir, file)
        try:
            return func(mode, fullname, *argrest)
        except error, e:
            tb = sys.exc_info()[2]
            if (e.errno != ENOENT and e.errno != ENOTDIR
                and saved_exc is None):
                saved_exc = e
                saved_tb = tb
    if saved_exc:
        raise error, saved_exc, saved_tb
    raise error, e, tb

def _os_spawnvp(mode, file, args):
    return os._spawnvpe(mode, file, args)

def _os_spawnvpe(mode, file, args, env):
    return os._spawnvpe(mode, file, args, env)

def _os_spawnlp(mode, file, *args):
    return os._spawnvpe(mode, file, args)

def _os_spawnlpe(mode, file, *args):
    return os._spawnvpe(mode, file, args[:-1], args[-1])

os._spawnvpe = _os__spawnvpe
os.spawnvp = _os_spawnvp
os.spawnvpe = _os_spawnvpe
os.spawnlp = _os_spawnlp
os.spawnlpe = _os_spawnlpe
os.__all__.extend(["spawnvp", "spawnvpe", "spawnlp", "spawnlpe"])

But the fact that I have to use similar code anywhere I need to use spawnlp is not fair. Notice that _spawnvpe is simply a clone of _execvpe from os.py, maybe if the problem is new API in c source, this approach could be used in os.py?

P.S. Although it's a bit stretching, one might also say that implementing spawnp on windows is not actually a new feature, and rather is a bugfix for misfeature. Why every other platform can benefit from spawnp and only Windows can't? This just makes os.spawnp useless: it becomes unreliable and can't be used in portable code at all.

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