Source code for pycopia.environ

# vim:ts=4:sw=4:softtabstop=4:smarttab:expandtab
# $Id: 396 2011-02-11 07:22:29Z keith.dart $
#    Copyright (C) 1999-2006  Keith Dart <>
#    This library is free software; you can redistribute it and/or
#    modify it under the terms of the GNU Lesser General Public
#    License as published by the Free Software Foundation; either
#    version 2.1 of the License, or (at your option) any later version.
#    This library is distributed in the hope that it will be useful,
#    but WITHOUT ANY WARRANTY; without even the implied warranty of
#    Lesser General Public License for more details.

Then environ module defines the Environ class. The Environ class simulates a
shell environment that provides methods analogous to shell commands that
manipulate the environment. Also, variable expansion is performed when setting
new values.


from __future__ import print_function

import os

import re
_var_re = re.compile(r'\$([a-zA-Z0-9_\?]+|\{[^}]*\})')
del re

[docs]class Environ(dict): """Environ is a dictionary (like os.environ) that does automatic variable expansion when setting new elements. It supports an extra method called 'export' that takes strings of the form 'name=value' that may be used to set assign variable names. The 'expand' method will return a string with variables expanded from the values contained in this object. """ def __setitem__(self, name, value): super(Environ, self).__setitem__(name, value) def __getattr__(self, name): return super(Environ, self).__getitem__(name) __setattr__ = __setitem__ def __delattr__(self, key): return super(Environ, self).__delitem__(key)
[docs] def inherit(self, env=None): """inherit([dict]) Works like the 'update' method, but defaults to updating from the system environment (os.environ).""" if env is None: env = os.environ self.update(env)
def set(self, val): self.__setitem__(name, self.expand(str(val)))
[docs] def export(self, nameval): """export('name=value') Works like the export command in the bash shell. assigns the name on the left of the equals sign to the value on the right, performing variable expansion if necessary. """ name, val = nameval.split("=", 1) self.__setitem__(name, self.expand(str(val))) return name
def __str__(self): s = map(lambda nv: "%s=%s" % (nv[0], nv[1]), self.items()) s.sort() return "\n".join(s)
[docs] def expand(self, value): """expand(string) Pass in a string that might have variable expansion to be performed (e.g. a section that has $NAME embedded), and return the expanded string. """ i = 0 while 1: m =, i) if not m: return value i, j = m.span(0) vname = if vname[0] == '{': vname = vname[1:-1] tail = value[j:] tv = self.get(vname) if tv is not None: # exand to empty if not found or val is None value = value[:i] + str(tv) else: value = value[:i] i = len(value) value = value + tail
def copy(self): return Environ(self)
if __name__ == "__main__": d = Environ() #d.inherit() d.export("HOME=/home/user") d.export("PKGHOME=/opt/pkg") d.export("PATH=$HOME/bin") d.export("PATH=$PATH:${PKGHOME}/bin") print (d) print ("-----") d["?"] = 0 print (d.expand("Here is the PATH: $PATH")) print (d.expand("$?"))