CODEWITHSUNDEEP
pythonlistmethods
user1816377
user1816377

Reputation: 245

sum for list of lists

I'm looking for method in python to sum a list of list that contain only integers. I saw that the method sum() works only for list but not for list of list. There is anything fit for me?

thank you

Upvotes: 2

Views: 12220

Answers (6)

Marcelo Moreira
Marcelo Moreira

Reputation: 81

import re
print sum( [int(i) for i in re.findall('[0-9]+', open("regex_sum_301799.txt").read()) ] )

Example File Source: http://python-data.dr-chuck.net/regex_sum_301799.txt

Upvotes: 0

Ashwini Chaudhary
Ashwini Chaudhary

Reputation: 251186

You can use sum() with a generator expression here:

In [18]: lis = [[1, 2], [3, 4], [5, 6]]

In [19]: sum(sum(x) for x in lis)
Out[19]: 21

or:

In [21]: sum(sum(lis, []))
Out[21]: 21

timeit comparisons:

In [49]: %timeit sum(sum(x) for x in lis)
100000 loops, best of 3: 2.56 us per loop

In [50]: %timeit sum(map(sum, lis))
100000 loops, best of 3: 2.39 us per loop

In [51]: %timeit sum(sum(lis, []))
1000000 loops, best of 3: 2.21 us per loop

In [52]: %timeit sum(chain.from_iterable(lis))       # winner 
100000 loops, best of 3: 1.43 us per loop

In [53]: %timeit sum(chain(*lis))
100000 loops, best of 3: 1.55 us per loop

Upvotes: 10

deepmynded
deepmynded

Reputation: 11

import re
#print sum( [ ****** *** * in **********('[0-9]+',**************************.read()) ] )

name = raw_input("Enter file:")
if len(name) < 1 : name = "sam.txt"
handle = open(name)
#handle = handle.read()
num = list()
total = 0
for line in handle:
    line = line.rstrip()
    if len(re.findall('([0-9]+)', line))== 0: continue
    num.append(re.findall('([0-9]+)', line))



print sum(sum(num,[]))

Upvotes: 0

Marcin
Marcin

Reputation: 49886

import itertools

sum(itertools.chain.from_iterable([[1,2],[3,4],[5,6]]))

itertools.chain flattens one level of iterable (which is all you need here), so sum gets the list with the sublists broken out.

Upvotes: 5

kevintodisco
kevintodisco

Reputation: 5191

l = [[1,2,3], [3,4,5], [3,5,6]]
total = sum([sum(x) for x in l])

Upvotes: 1

Nick ODell
Nick ODell

Reputation: 25474

sum(map(sum, my_list))

This runs sum on every element of the first list, then puts the results from those into sum again.

Upvotes: 2

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