[python-tip] Properties

[wtd]

Frequently I see code like the following.

code:

class Foo(object):     def __init__(self, bar):         self.bar = bar     def get_bar(self):         return self.bar     def set_bar(self, bar):         self.bar = bar f = Foo(42) print f.get_bar() f.set_bar(37) print f.get_bar()

Now, obviously we don't need get_bar in this case because the bar field is public. The set_bar function is not strictly necessary either.

But, making attributes of an object private is a good idea, so...

code:

class Foo(object):     def __init__(self, bar):         self.__bar = bar     def get_bar(self):         return self.__bar     def set_bar(self, bar):         self.__bar = bar f = Foo(42) print f.get_bar() f.set_bar(37) print f.get_bar()

But now our code has to look all Java-like with explicit setters and getters. Ugly.

What if we could keep the attribute private but still use:

code:

f = Foo(42) print f.bar f.bar = 37 print f.bar

There is!

code:

class Foo(object):     def __init__(self, bar):         self.__bar = bar     def __get_bar(self):         return self.__bar     def __set_bar(self, bar):         self.__bar = bar     bar = property(__get_bar, __set_bar)

Use your new power responsibly.