Thursday, April 7, 2011


As a professionally-oriented blog, and moreover, a software oriented one, this will be terse and to the point. Personal details will be kept to a minimum, software details will be explored at a significant depth.

For my first post, I'd like to describe a rather simple, and no-doubt popular technique that I have been using recently while coding in python. This technique is what I call a 'keyword argument'. Inspired by the type of argument in python that can be passed to a function as follows:

def foo(**kwargs):
    for (key,value) in kwargs.items():
        print "%s for %s" % (key,value)
if __name__ == "__main__":
    foo(a = 1, b = 2, c = 3)
the output of this program is of course (or some permutation of the following): 
a for 1
c for 3 
b for 2
now what is interesting about this idea? It is a fairly standard way of passing variable-length arguments where values are assigned to variables. The way it has interested me is to borrow this kind of pattern, except instead of using a dictionary built by the python interpreter out of arguments to a function, I use a "command" function which builds this dictionary from some input. A simplified version is as follows (please ignore the naive regex):

def command(self, command_string):
    command_root = re.findall(r"^(\w+)",command_string)
    key_argument_tuples = re.findall(r"--([\w]+)=([^ ^=]+)",command_string)
    for x in key_args:
        cmd_dict[x[0]] = x[1]

this is an extremely simple way (through the use of first-class functions) to build arguments for functions through a generic interface. I will clarify the part about first-class functions (self.function_dict) in my next post.

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