对列表中所有元素求和，除了第一个

Question

Add all the elements in the list of lists except the first element and make a new list.

  l = [[u'Security', -604.5, -604.5, -604.5, 
       -302.25, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, -2115.75], 
       [u'Medicare', -141.38, -141.38, -141.38, -70.69, 
       0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, -494.83], 
       [u'Insurance', -338.0, -338.0, -338.0, -169.0, 0.0, 
       0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, -1183.0]]

Output should look like

['total',-1083.88,-1083.88,-1083.88,-541.94,0.0,0.0,0.0,0.0,0.0,0.0,
   0.0,0.0,-3793.58]

Eg: -1083.88 of the output list is = -604.5+(-141.38)+(-338.0)=-1083.88

I've tried like this

for i in r:
   del(i[0])
total = [sum(i) for i in zip(*r)]

Answer 1

Going by your expected output, I believe you're looking for a transposition and sum on the columns. You can use zip for that.

r = [sum(x) if not isinstance(x[0], str) else 'total' for x in zip(*l)]

print(r)
['total', -1083.88, -1083.88, -1083.88, -541.94, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, -3793.58]

---

Alternatively, convert the transposal to a list and you can avoid the if check (this is similar to MaximTitarenko's answer , so credit to them as well).

r = [sum(x) for x in list(zip(*l))[1:]]
r.insert(0, 'total')

Or, if you'd prefer,

r = ['total'] + [sum(x) for x in list(zip(*l))[1:]]

Which is a little less elegant.

Answer 2

You can try this:

result = ['total'] + [sum(el) for el in list(zip(*l))[1:]] 

print(result)
# ['total', -1083.88, -1083.88, -1083.88, -541.94, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, -3793.58]

Answer 3

To use all python flavour you need to use itertools.islice since in Python zip() returns iterator and you cannot just [1:] subscript zip object.

In [1]: l = [[u'Security', -604.5, -604.5, -604.5,
   ...:    ...:        -302.25, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, -2115.75
   ...: ],
   ...:    ...:        [u'Medicare', -141.38, -141.38, -141.38, -70.69,
   ...:    ...:        0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, -494.83],
   ...:    ...:        [u'Insurance', -338.0, -338.0, -338.0, -169.0, 0.0,
   ...:    ...:        0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, -1183.0]]
   ...:

In [2]: from itertools import islice

In [3]: total = [sum(new) for new in islice(zip(*l), 1, None)]

In [4]: total
Out[4]:
[-1083.88, -1083.88, -1083.88, -541.94, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, -3793.58]

To include 'total' in the begging as cᴏʟᴅsᴘᴇᴇᴅ kindly noted in comments

In [5]: ['total'] + total
Out[6]:
    ['total', -1083.88, -1083.88, -1083.88, -541.94, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, -3793.58]

Answer 4

If you want to be really efficient about it, you could use itertools' islice

from itertools import islice, repeat
s = map(sum, zip(*map(islice, l, repeat(1), repeat(None) ) ) )
total = ['total']
total.extend(s)

Edit: sorry, didn't read the entire context the first time around :)