As mentioned in the introduction to this module the challenges in data processing are usually posed by the data rather than the processing algorithms.
For example you will have to deal with the possibility that you cannot read one of the files. This could happen if you do not have permissions to read the file, if the file does not exist, etc. How could one of the files not exist? It could be because it actually doesn't exist (perhaps the volunteer forgot to copy it onto the flashdrive being used), or perhaps it appears to your program not to exist because they typed its name in incorrectly. At any rate you need to, at best, help them out, and, at least, fail gracefully with an explanation.
Similarly you'll have to ensure that the files are properly formatted, for example that each record in the contestant file does contain the number fields you expect it to, not more, and not less. Let's say you opt to split a line to get the field values, e.g. running
(number, last_name, first_name) = split(line)
will produce an error if the value of line is
"Topper,Tim",
>>> (number, first_name, last_name) = 'Topper,Tim'.split(',')
Traceback (most recent call last):
File "< pyshell#1>", line 1, in < module>
(number, first_name, last_name) = 'Topper,Tim'.split(',')
ValueError: need more than 2 values to unpack
>>>
But a "naive" user should not be confronted with a Python error message.
There are two programming approaches to dealing with potential error situations. One is anticipatory, the other is reactive.
In the anticipatory approach you check that there is an object with the name you were given, that it is a file (not a directory, or link, etc.), that you have permisson to open it and so on.
In the reactive approach you try to open it and then deal with an error if one results by "catching exceptions".
Which approach should be preferred is a subject of active debate in the programming community*, but one approach often dominates the other in particular languages. The anticipatory approach is prevalent in the C community, while the reactive approach is more common in the Python community. See the next page, Python Exceptions, for the syntactical details about working with Python's exceptions.
* A readable entry to the debate is Joel Spolsky' spiece titled simply Exceptions. Searching for reactions to the piece will lead you to the other side of the debate.