Saves the name of the managed attribute and uses the saved name in calls to the getter, setter, or destructor. This allows the same function to be used for more than one managed variable. <br> Using property() with more than one variable results in many lines of duplicate code for the individual getters, setters, and destructors. This recipe shows how to reuse these functions for multiple variables. Also, it provides default functions so that the only the interesting functions need to be specified.
Python, 75 lines
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Copy to clipboard1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 | class CommonProperty(object):
"""A more flexible version of property()
Saves the name of the managed attribute and uses the saved name
in calls to the getter, setter, or destructor. This allows the
same function to be used for more than one managed variable.
As a convenience, the default functions are gettattr, setattr,
and delattr. This allows complete access to the managed
variable. All or some of those can be overridden to provide
custom access behavior.
"""
def __init__(self, realname, fget=getattr, fset=setattr, fdel=delattr, doc=None):
self.realname = realname
self.fget = fget
self.fset = fset
self.fdel = fdel
self.__doc__ = doc or ""
def __get__(self, obj, objtype=None):
if obj is None:
return self
if self.fget is None:
raise AttributeError, "unreadable attribute"
return self.fget(obj, self.realname)
def __set__(self, obj, value):
if self.fset is None:
raise AttributeError, "can't set attribute"
self.fset(obj, self.realname, value)
def __delete__(self, obj):
if self.fdel is None:
raise AttributeError, "can't delete attribute"
self.fdel(obj, self.realname, value)
## Example of requiring password access to view selected attributes
class SecurityError(Exception): pass
def securitycheck(*args):
"Stub function. A real check should be a bit more thorough ;)"
return True
class Employee(object):
__authenticate = False
def __init__(self, name, dept, salary, age):
self.name=name
self.dept=dept
self._salary = salary
self._age = age
def authorize(self, userid, password):
if securitycheck(userid, password):
self.__authenticate = True
def passwordget(self, name):
if not self.__authenticate:
raise SecurityError, "Viewing secure data requires valid password"
return getattr(self, name)
salary = CommonProperty('_salary', passwordget, None, None, doc="Annual Salary")
age = CommonProperty('_age', passwordget, None, None, doc="Age as of 1 Jan 2003")
manager = Employee('Raymond', 'PySystemsGroup', 'ProBono', 38)
manager.authorize('Guido', 'omega5')
print manager.name
print manager.salary
|
Tags: shortcuts
