[Chicago] Frame Hacks Lightning Talk Code

[Feihong Hsu]

Because I didn't get to type it out in front of everyone, I'm posting the example where I use frame manipulation to generate properties on a class.

Warning: The following code may crash your computer if you allow a strange Asian man with a unique electromagnetic aura to type it in using your keyboard.

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# As a fun experiment, change the Employee class so that it doesn't inherit
# from object (that makes it an old-style class). Observe the weird side
# effects, then make an angry post on your blog!

import sys

# Pretend this class was implemented in C++ and has a really annoying interface
# with a ton of getter and setter method.
class Employee(object):
    def __init__(self, given_name, family_name, date_of_birth):
        self.given_name = given_name
        self.family_name = family_name
        self.date_of_birth = date_of_birth

    def GetGivenName(self): return self.given_name
    def SetGivenName(self, value):  self.given_name = value
    
    def GetFamilyName(self): return self.family_name
    def SetFamilyName(self, value):  self.family_name = value
    
    def GetDateOfBirth(self): return self.date_of_birth
    def SetDateOfBirth(self, value):  self.date_of_birth = value
    # ad infinitum...

def properties(*args):
    framedict = sys._getframe(1).f_locals

    for propname, realname in args:
        framedict[propname] = property(
            fget=eval("lambda self: self.Get%s()" % realname),
            fset=eval("lambda self, value: self.Set%s(value)" % realname)
        )

# Let's make a nice wrapper for the Employee class that uses properties in
# place of the getter and setter methods. Also, let's shorten the names
# because we're lazy and don't like to type too much.
class PyEmployee(Employee):
    properties(
        ('given', 'GivenName'),
        ('family', 'FamilyName'),
        ('birth', 'DateOfBirth'),
    )

if __name__ == '__main__':
    e = PyEmployee('Feihong', 'Hsu', '2007-11-15')
    print e.given, e.GetGivenName(), e.given_name
    e.given = 'Horatio'     # change given name through the property
    print e.given, e.GetGivenName(), e.given_name



       
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