CODEWITHSUNDEEP
pythondictionarycounter
von Mises
von Mises

Reputation: 266

Update Nested Counter in a Dictionary

I am going through a large CSV file line by line. What I want to do is count occurrences of the strings in a certain column. Where I am running into trouble is that I would like the counter to be nested inside of a dictionary, where the keys for the outer dictionary is the value from another column. I need to do this or else the data will be processed incorrectly as there are duplicates.

imagine my CSV:

outerDictKey    CounterKey
apple     purple
apple     blue
pear    purple

So basically I want:

dictionary = { apple:
                    counter({blue: 1
                     purple: 1})
                pear:
                   counter({purple: 1})
             }

I wasnt sure how to do this.

myCounter = Counter()
myKey = 'barbara'
counterKey = 'streisand'
largeDict = defaultdict(dict)       
largeDict[myKey] = {myCounter[counterKey] += 1}

Intuitively this looks like it wouldnt work, and of course it gives a syntax error.

I also tried

largeDict[myKey][myCounter][counterKey]+=1

Which throws a "TypeError: unhashable type: 'Counter'" error.

Finally

>>> largeDict[myKey]=Counter()
>>> largeDict[myKey][myCounter][counterKey]+=1

Which still gives a type error. So how do I increment a Counter nested in a dictionary?

Upvotes: 2

Views: 3583

Answers (2)

Marcin
Marcin

Reputation: 49826

This will work:

myCounter = Counter()
largedict = { myKey:
                    {counterKey: myCounter
                     anotherKey: Value2}
             }

largedict[myKey][counterKey]['somethingyouwanttocount']+=1

Counter is just a dict with some extra functionality. However, as a dict, it cannot be a key in a dict, nor an entry in a set, which explains the unhashable exception.

Alternatively, if you're keeping track of information about coherent entities, rather than using nested dicts, you could store the information (including the counter) in objects, and put the objects in a dict as necessary.

If every value is a counter, then just use defaultdict:

from collections import defaultdict, Counter
largedict = defaultdict(Counter)
largedict['apple']['purple']+=1

Upvotes: 7

thefourtheye
thefourtheye

Reputation: 239473

If you just want to count occurrences of the strings in a certain column, wouldnt this be enough

import collections
data = "Welcome to stack overflow. To give is to get."

print collections.Counter(data.split())

Output

Counter({'to': 2, 'give': 1, 'get.': 1, 'is': 1, 'Welcome': 1, 'To': 1, 'overflow.': 1, 'stack': 1})

Upvotes: 1

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