Python 101: How to Change a Dict Into a Class

I work with a lot of dictionaries at my job. Sometimes the dictionaries get really complicated with lots of nested data structures embedded within them. Recently I got a little tired of trying to remember all the keys in my dictionaries so I decided to change one of my dictionaries into a class so I could access the keys as instance variables / attributes. If you’ve ever gotten sick

Here’s one simple way to do it:

########################################################################
class Dict2Obj(object):
    """
    Turns a dictionary into a class
    """
 
    #----------------------------------------------------------------------
    def __init__(self, dictionary):
        """Constructor"""
        for key in dictionary:
            setattr(self, key, dictionary[key])
 
 
#----------------------------------------------------------------------
if __name__ == "__main__":
    ball_dict = {"color":"blue",
                 "size":"8 inches",
                 "material":"rubber"}
    ball = Dict2Obj(ball_dict)

This code uses setattr to add each of the keys as attributes to the class. The following shows some examples of how it works:

>>> ball.color
'blue'
>>> ball.size
'8 inches'
>>> print ball
<__main__.Dict2Obj object at 0x028CD5B0>

When we print the ball object, we get a rather unhelpful string back from the class. Let’s override the __repr__ method of our class and make it print out something a little more useful:

########################################################################
class Dict2Obj(object):
    """
    Turns a dictionary into a class
    """
 
    #----------------------------------------------------------------------
    def __init__(self, dictionary):
        """Constructor"""
        for key in dictionary:
            setattr(self, key, dictionary[key])
 
    #----------------------------------------------------------------------
    def __repr__(self):
        """"""
        return "<Dict2Obj: %s>" % self.__dict__
 
#----------------------------------------------------------------------
if __name__ == "__main__":
    ball_dict = {"color":"blue",
                 "size":"8 inches",
                 "material":"rubber"}
    ball = Dict2Obj(ball_dict)

Now if we print out the ball object, we’ll get the following:

>>> print ball
<Dict2Obj: {'color': 'blue', 'material': 'rubber', 'size': '8 inches'}>

This is a little unintuitive in that it is printing out a dictionary using the class’s internal __dict__ rather than just the attribute names. This is more a matter of taste than anything, but let’s try to get just the method names:

########################################################################
class Dict2Obj(object):
    """
    Turns a dictionary into a class
    """
 
    #----------------------------------------------------------------------
    def __init__(self, dictionary):
        """Constructor"""
        for key in dictionary:
            setattr(self, key, dictionary[key])
 
    #----------------------------------------------------------------------
    def __repr__(self):
        """"""
        attrs = str([x for x in self.__dict__])
        return "<Dict2Obj: %s>" % attrs
 
#----------------------------------------------------------------------
if __name__ == "__main__":
    ball_dict = {"color":"blue",
                 "size":"8 inches",
                 "material":"rubber"}
    ball = Dict2Obj(ball_dict)

Here we just loop over the contents of __dict__ and return a string with just a list of the keys, which match up with the attribute names. You could have also done it like this:

attrs = str([x for x in dir(self) if "__" not in x])

I’m sure there are lots of other ways to accomplish this sort of thing as well. Regardless, I found this little piece of code helpful in some of my work. Hopefully you’ll find it useful too.