Trying To Add To Dictionary Values By Counting Occurrences In A List Of Lists (python)

I'm trying to get a count of items in a list of lists and add those counts to a dictionary in Python. I have successfully made the list (it's a list of all possible combos of occur

Solution 1:

Use a Counter instead of an ordinary dict to count things:

from collections importCountershowcount= Counter()
for item in recs:
    showcount.update(item)

or even:

from collections importCounterfrom itertools import chain

showcount = Counter(chain.from_iterable(recs))

As you can see that makes your code vastly simpler.

Solution 2:

If all you want to do is flatten your list of lists you can use itertools.chain()

>>>import itertools>>>listOfLists = ((1,3,4),(1,2,4),(1,4),(1,2),(1,4)) >>>flatList = itertools.chain.from_iterable(listOfLists)

The Counter object from the collections module will probably do the rest of what you want.

>>>from collections import Counter>>>Counter(flatList)
Counter({1: 5, 4: 4, 2: 2, 3: 1})

Solution 3:

I have some old code that resembles the issue, it might prove useful to people facing a similar problem.

import sys
file = open(sys.argv[-1], "r").read()
wordictionary={}
for word in file.split():
    if word notin wordictionary:
        wordictionary[word] = 1else:
        wordictionary[word] += 1
sortable = [(wordictionary[key], key) for key in wordictionary]
sortable.sort()
sortable.reverse()
for member in sortable: print (member)

Solution 4:

First, 'flatten' the list using a generator expression: (item for sublist in combs for item in sublist).

Then, iterate over the flattened list. For each item, you either add an entry to the dict (if it doesn't already exist), or add one to the value.

d = {}
for key in (item for sublist in combs for item in sublist):
    try:
        d[key] += 1except KeyError:  # I'm not certain that KeyError is the right one, you might get TypeError. You should check this
        d[key] = 1

This technique assumes all the elements of the sublists are hashable and can be used as keys.