Python shell that doesn't work

s.py

#!/usr/bin/python

import os
from subprocess import call
import subprocess as sp

class _cmd (object):
  def __init__(self, sh, cmd):
    self.c = cmd
    self.sh = sh
  def __call__(self, *p, **kw):
    print self.c, p
    rt = call ([self.c] + list(p))
    self.sh.setenv({'?' : rt})

def cmd_split(s):
  l = s.split(' ')
  # FIXME quoting here
  print l
  return l

def env_cat(**kw):
  r = ''
  for k in kw:
    r += '%s=%s '%(str(k), str(kw[k]))
  return r

class sh(object):
  def __init__(self):
    pass
  def __getattr__(self, name):
    # FIXME dir(_) etc won't work
    return _cmd(self, name)
  def __dir__(self):
    return object.__dir__(self)
  def __call__(self, *p, **env):
    if len(p) == 1:
      p = cmd_split (p[0])
      call (p, env=env)
  def cd(self, d):
    os.chdir(d)
    return self
  def setenv(self, *envmap, **kw):
    if len(envmap) == 1 and type(envmap[0]) == type({}):
      for k in envmap[0]:
        os.environ[k] = str(envmap[0][k])
    for k in kw:
      os.environ[k] = str(kw[k])
    return self
  def env(self, *k, **ev):
    if len(ev) == 0:
      for _k in k:
        print '%s=%s' % (_k, os.environ[_k] if _k in os.environ else '')
    else: 
      os.system('/usr/bin/env ' + env_cat(**ev) + k[0])

_ = sh()

def usage():
  return '''
from s import _
_.cd('/tmp').ls()
_('ls /tmp')
'''