How do I create a list or set object in a class in Python?
- by Az
For my project, the role of the Lecturer (defined as a class) is to offer projects to students. Project itself is also a class. I have some global dictionaries, keyed by the unique numeric id's for lecturers and projects that map to objects.
Thus for the "lecturers" dictionary (currently):
lecturer[id] = Lecturer(lec_name, lec_id, max_students)
I'm currently reading in a white-space delimited text file that has been generated from a database. I have no direct access to the database so I haven't much say on how the file is formatted. Here's a fictionalised snippet that shows how the text file is structured. Please pardon the cheesiness.
0001 001 "Miyamoto, S." "Even Newer Super Mario Bros"
0002 001 "Miyamoto, S." "Legend of Zelda: Skies of Hyrule"
0003 002 "Molyneux, P." "Project Milo"
0004 002 "Molyneux, P." "Fable III"
0005 003 "Blow, J." "Ponytail"
The structure of each line is basically proj_id, lec_id, lec_name, proj_name.
Now, I'm currently reading the relevant data into the relevant objects. Thus, proj_id is stored in class Project whereas lec_name is a class Lecturer object, et al. The Lecturer and Project classes are not currently related.
However, as I read in each line from the text file, for that line, I wish to read in the project offered by the lecturer into the Lecturer class; I'm already reading the proj_id into the Project class. I'd like to create an object in Lecturer called offered_proj which should be a set or list of the projects offered by that lecturer. Thus whenever, for a line, I read in a new project under the same lec_id, offered_proj will be updated with that project. If I wanted to get display a list of projects offered by a lecturer I'd ideally just want to use print lecturers[lec_id].offered_proj.
My Python isn't great and I'd appreciate it if someone could show me a way to do that. I'm not sure if it's better as a set or a list, as well.
Update
After the advice from Alex Martelli and Oddthinking I went back and made some changes and tried to print the results.
Here's the code snippet:
for line in csv_file:
proj_id = int(line[0])
lec_id = int(line[1])
lec_name = line[2]
proj_name = line[3]
projects[proj_id] = Project(proj_id, proj_name)
lecturers[lec_id] = Lecturer(lec_id, lec_name)
if lec_id in lecturers.keys():
lecturers[lec_id].offered_proj.add(proj_id)
print lec_id, lecturers[lec_id].offered_proj
The print lecturers[lec_id].offered_proj line prints the following output:
001 set([0001])
001 set([0002])
002 set([0003])
002 set([0004])
003 set([0005])
It basically feels like the set is being over-written or somesuch. So if I try to print for a specific lecturer print lec_id, lecturers[001].offered_proj all I get is the last the proj_id that has been read in.
