How to add property to a class dynamically?

Question

The goal is to create a mock class which behaves like a db resultset.

So for example, if a database query returns, using a dict expression, {\'ab\':100, \'cd\'

Answer 1

Here is a solution that:

• Allows specifying property names as strings, so they can come from some outside data source instead of all being listed in your program.
• Adds the properties when the class is defined, instead of every time an object is created.

After the class has been defined, you just do this to add a property to it dynamically:

setattr(SomeClass, 'propertyName', property(getter, setter))

Here is a complete example, tested in Python 3:

#!/usr/bin/env python3

class Foo():
  pass

def get_x(self):
  return 3

def set_x(self, value):
  print("set x on %s to %d" % (self, value))

setattr(Foo, 'x', property(get_x, set_x))

foo1 = Foo()
foo1.x = 12
print(foo1.x)