Generating Possible Courses to Fulfill Prerequisites

Nov 06 2010

For this part of the project, the goal is to generate a list of courses that meets the requirements for a course from a string stored in the database in a specific format. The entire project was designed so that each component is modular. This way, each component could be written and tested independently, and the complexity of the task is greatly reduced. Likewise, the project consists of so many high level components it appears, at first glance, to be incapable of being one piece. To my surprise, I put together Scrapy + PLY + Django, and it all works beautifully.

Part of the reason these separate components can all come together is that the specifications were set in stone before design, and the design itself (choosing the web framework, scraper, compiler) is tailored with the whole in mind. So for this part, these are the requirements:

From a string of prerequisites separated by commas, with alternatives separated by slashes, generate a list of lists that represents all possible course combinations, without more than one course selected out of each group of alternatives.

"CS 241, STAT 206/STAT 230/STAT 240" -> [['CS 241'], [' STAT 206', 'STAT 230', 'STAT 240']]
[['CS 241'], [' STAT 206', 'STAT 230', 'STAT 240']] -> [('CS 241', 'STAT 206'), ('CS 241', 'STAT 230'), ('CS 241', 'STAT 240')]

Basically, it’s a combination of a list of lists of strings.

Once the goal was set, the coding phase was straightforward. Simply understand the meaning of the input, and use a python function to turn it into the specified output.

def calc_comb(t):
    l = t.split(', ')
    group = []
    for s in l:
    return list(itertools.product(*group))


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