Python many-to-one mapping (creating equivalence classes)
- by Adam Matan
Hi,
I have a project of converting one database to another. One of the original database columns defines the row's category. This coulmn should be mapepd to a new category in the new databse.
For example, let's assume the original categories are:parrot, spam, cheese_shop, Cleese, Gilliam, Palin
Now that's a little verbose for me, And I want to have these rows categorized as sketch, actor - That is, define all the sketches and all the actors as two equivalence classes.
>>> monty={'parrot':'sketch', 'spam':'sketch', 'cheese_shop':'sketch',
'Cleese':'actor', 'Gilliam':'actor', 'Palin':'actor'}
>>> monty
{'Gilliam': 'actor', 'Cleese': 'actor', 'parrot': 'sketch', 'spam': 'sketch',
'Palin': 'actor', 'cheese_shop': 'sketch'}
That's quite awkward- I would prefer having something like:
monty={ ('parrot','spam','cheese_shop'): 'sketch',
('Cleese', 'Gilliam', 'Palin') : 'actors'}
But this, of course, sets the entire tuple as a key:
>>> monty['parrot']
Traceback (most recent call last):
File "<pyshell#29>", line 1, in <module>
monty['parrot']
KeyError: 'parrot'
Any ideas how to create an elegant many-to-one dictionary in Python?
Thanks,
Adam
