Grouping tuples using libraries in Python

Question

Using Python is there an easier way without writing bunch of loops be able to count the values in a similar way. Perhaps using some library such as itertools groupby?

#original tuple array
[("A","field1"),("A","field1"),("B","field1")]

#output array
[("A","field1", 2), ("B", "field1",1)]

So you just want the count? Try using `collections.Counter`. Have you actually *tried* `groupby`? — jonrsharpe, Aug 19 '15 at 09:03

score 4 · Accepted Answer · answered Aug 19 '15 at 09:04

4

You can use a Counter dict to group, adding the count at the end

l = [("A","field1"),("A","field1"),("B","field1")]


from collections import Counter


print([k+(v,) for k,v in Counter(l).items()])

If you want the output ordered by the first time you encounter a tuple, you can use an OrderedDict to do the counting:

from collections import OrderedDict

d = OrderedDict()
for t in l:
    d.setdefault(t, 0)
    d[t] += 1

print([k+(v,) for k,v in d.items()])

answered Aug 19 '15 at 09:04

Padraic Cunningham

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Awesome, I like OrderedDict() it removes the need to presort the array! Thanks a bunch! – codeBarer Aug 19 '15 at 09:14

tobias_k · Answer 2 · 2015-08-19T09:03:59.623

0

You can use itertools.groupby. Omit the key parameter, then it will just group equal elements (assuming those are consecutive), then add the number of elements in the group.

>>> lst = [("A","field1"),("A","field1"),("B","field1")]
>>> [(k + (len(list(g)),)) for k, g in itertools.groupby(lst)]
[('A', 'field1', 2), ('B', 'field1', 1)]

If the elements are not consecitive, then this will not work, and anyway, the solution suggesting collections.Counter seems to be a better fit to the problem.

edited Aug 19 '15 at 09:03

answered Aug 19 '15 at 09:02

tobias_k

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Data must be in sorted order or else this will fail – Padraic Cunningham Aug 19 '15 at 09:03
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Thanks, I like this solution but the data needs to be sorted. I guess for large lists this might be slower because of sorting. – codeBarer Aug 19 '15 at 09:10

score 0 · Answer 3 · edited May 23 '17 at 11:58

0

I guess you just want to count the number of ocurrences of each tuple...right? If so, you can use Counter

edited May 23 '17 at 11:58

Community

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answered Aug 19 '15 at 09:03

manu

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Hi Manu, yet I'm just doing a count. I want to count total of field1 that have "A" and count total field1 in "B" – codeBarer Aug 19 '15 at 09:04

Grouping tuples using libraries in Python

3 Answers3