import sys
def attribute(attrname, permit='rwd', fget=None, fset=None, fdel=None, doc=''):
"""returns a property associated with 'attrname'.
By default, a simple property with get, set, and delete methods
will be created. Optionally, specific get/set/del methods may be
supplied. You can also choose to omit the creation of one or more
of the default get/set/del methods via the 'permit' flag:
'r': readable, 'w':writable, 'd':deletable
So, if you want a property that is readable and deletable, but not
writable, use "permit='rd'".
"""
if _isprivate(attrname):
attrname = _mangle(_get_classname(), attrname)
if 'r' in permit and fget is None:
fget = lambda self: getattr(self, attrname)
if 'w' in permit and fset is None:
fset = lambda self, value: setattr(self, attrname, value)
if 'd' in permit and fdel is None:
fdel = lambda self: delattr(self, attrname)
return property(fget, fset, fdel, doc)
def _isprivate(attrname):
return attrname.startswith("__") and not attrname.endswith("__")
def _mangle(classname, attrname):
'''mangles name according to python name-mangling
conventions for private variables'''
return "_%s%s" % (classname, attrname)
def _get_classname():
"returns the calling class' name"
frame = sys._getframe(2)
classname = frame.f_code.co_name
return classname
# example
if __name__ == "__main__":
class C(object):
a = attribute('_a', fget=lambda self: self._a*2)
def __init__(self):
self._a = "A"
c = C()
print c.a # uses a.fget, user supplied
c.a = "AA" # uses a.fset, provided by default
print c.a
