[Tutor] how can I use Set.interaction function on a dictionary

[Alan Gauld]

> 1. I have a dictionary with 4 keys and some repeated
> values for each key.
> 
>>>> dida
> {'NM_001033044': [32842023, 32842023, 32842023,
> 32842023, 32842023, 32842023, 32842023, 32842023,
> 32842023, 32842023, 32842023, 32842023, 32843894,
> 32843894, 32843894, 32843894, 32843894, 32843894,
> 32843894, 32843894, 32843894, 32843894, 32844846,
> 32844846, 32844846, 32844846, 32844846, 32844846,
> 32844846, 32844846, 32844846, 32844846, 32845745],

>>>> didi
> {'NM_001033044': [32842023, 32843894, 32844846,
> 32845745], 'NM_002065': [32844846, 32842023, 32845745,
> 32843894], 'NM_015701': [32844783], 'NM_001033056':
> [32843894, 32844846, 32845745, 32842023]}
> 
> Question:
> 
> 1. How can I get A^B^C^D(^ = intersection) where A, B,
> C and D are keys from dida or didi.

I assume the value of A,B etc are the lists of data purged 
of duplicates? And you now want to find the common elements 
across all four sets?

> 2. How can I store values generated dynamically. For
> example, here in 'dida' I know there are 4 keys, but
> how can I create 4 lists while running in for loop and
> store the key values in 'dida'. 

I'm not sure what the problem is here:

len(dida.keys())

Will give the number of keys, and

dida[key] will give you the list.

But I think you know enough Python for that to be too simple.
Can you elaborate further?

> Do I have to write an class object that will create
> empty lists depending on number of keys a dictionary
> has?
> 
> I am loosing my mind because I do not know how to
> store the values for each key in a loop and do set
> operations.

mysets = []
for value in dida.itervalues():
     mysets.append(set(value))

Gives you a list of 4 sets.

You can get the intersect of 4 sets by taking the intersects 
of two at a time:
 
result = mysets[0]
for s in mysets[1:]
    result = result.intersection(s)

>>>> for m in range(len(didi.keys())):
> ...     x = m+1
> ...     a = Set(didi[didi.keys()[m]])

Any time you use len() in a for loop you should ask whether 
thats really the best way. And if you then use the index to get 
the items, ask again.

> I would be happy, if I could store all 4 sets
> (above)into listsor sets A, B, C and D and do 
> (A^B)^(C^D).

See my code above which gives you a list of 4 sets.

Alan G
Author of the learn to program web tutor
http://www.freenetpages.co.uk/hp/alan.gauld