CODEWITHSUNDEEP
pythondictionary
user1189851
user1189851

Reputation: 5041

Count of values for each distinct key

My python code is like this:

d={'abc':'movies', 'abc': 'sports', 'abc': 'music', 'xyz': 'music', 'pqr':'music','pqr':'movies', 'pqr':'sports', 'pqr':'news', 'pqr':'sports'}

b=[j[0] for i in d for j in i.items()]

for k in list(set(b)):
    print "{0}: {1}".format(k, b.count(k))

I need to print number of distinct values per each key individually. That means I would want to print

abc 3
xyz 1
pqr 4

I get an error: AttributeError: 'str' object has no attribute 'items' Please help!

Upvotes: 0

Views: 127

Answers (2)

pradyunsg
pradyunsg

Reputation: 19406

You cannot have duplicate keys in a dictionary in Python:

>>> d = {'abc':'movies', 'abc': 'sports', 'abc': 'music', 'xyz': 'music', 'pqr':'music','pqr':'movies', 'pqr':'sports', 'pqr':'news', 'pqr':'sports'}
>>> print d
{'pqr': 'sports', 'abc': 'music', 'xyz': 'music'}

Upvotes: 1

Bakuriu
Bakuriu

Reputation: 101909

You can't do that, because each key can appear only once in a dictionary:

>>> d={'abc':'movies', 'abc': 'sports', 'abc': 'music', 'xyz': 'music', 'pqr':'music','pqr':'movies', 'pqr':'sports', 'pqr':'news', 'pqr':'sports'}
>>> d
{'pqr': 'sports', 'abc': 'music', 'xyz': 'music'}

What you want is to have lists as values:

>>> d = {'abc': ['movies', 'sports', 'music'], 'xyz': ['music'], 'pqr': ['music', 'movies', 'sports', 'news', 'sports']}
>>> d
{'xyz': ['music'], 'abc': ['movies', 'sports', 'music'], 'pqr': ['music', 'movies', 'sports', 'news', 'sports']}

With this representation it's pretty simple to do what you want:

>>> for key, value in sorted(d.items()):
...     print key, len(value)   #in python3: print(key, len(value))
... 
abc 3
pqr 5
xyz 1

If you then want to add a value to a given key simply do:

>>> d['xyz'].append('news')
>>> for key, value in sorted(d.items()):
...     print key, len(value)
... 
abc 3
pqr 5
xyz 2

Often in this kind of circumstances using a defaultdict instead of a plain dict is better.

Upvotes: 7

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