CODEWITHSUNDEEP
pythonpropertiessetattr
Pablo Fernandez
Pablo Fernandez

Reputation: 287520

How to create a property with its name in a string?

Using Python I want to create a property in a class, but having the name of it in a string. Normally you do:

blah = property(get_blah, set_blah, del_blah, "bleh blih")

where get_, set_ and del_blah have been defined accordingly. I've tried to do the same with the name of the property in a variable, like this:

setattr(self, "blah", property(self.get_blah, self.set_blah, self.del_blah, "bleh blih"))

But that doesn't work. The first case blah returns the value of the property, on the second case, it returns a property, that is <property object at 0xbb1aa0>. How should I define it so it works?

Upvotes: 3

Views: 405

Answers (3)

Juergen
Juergen

Reputation: 12728

As much I would say, the difference is, that in the first version, you change the classes attribute blah to the result of property and in the second you set it at the instance (which is different!).

How about this version:

setattr(MyClass, "blah", property(self.get_blah, self.set_blah,
        self.del_blah, "bleh blih"))

you can also do this:

setattr(type(self), "blah", property(self.get_blah, self.set_blah,
        self.del_blah, "bleh blih"))

Upvotes: 2

Andre Miller
Andre Miller

Reputation: 15493

If I understand what you're trying to do, you could accomplish it by overriding the class's getattr and setattr methods.

For example:

class Something(object):
    def __getattr__(self, name):
        # The name of the property retrieved is a string called name
        return "You're getting %s" % name

something = Something()

print something.foo
print something.bar

Will print:

You're getting foo
You're getting bar

This way you can have a generic getter and setter that has the name of the property in a string and does something with it accordingly.

Upvotes: 1

Martin v. L&#246;wis
Martin v. L&#246;wis

Reputation: 127467

One way is to write into locals():

class X:
    for attr in ["a","b","c"]:
        def getter(self, name=attr):
            return name+"_value"
        locals()[attr] = property(getter, None, None, attr)

x = X()
print x.a
print x.b
print x.c

gives

a_value
b_value
c_value

Upvotes: 1

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