klim@moose:~> python
Python 2.5.2 (r252:60911, Mar  1 2008, 13:52:45) 
[GCC 4.2.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> a = {}                    <----- an empty dictionary
>>> a['klim'] = 100           <----- (key,value) = ('klim', 100) is added
>>> a['oak'] = 20             <----- another pair is added
>>> for k in a.keys():        <----- iterates through all keys 
...   print k
... 
klim
oak
>>> a['klim'] += 200          <----- update the value 
>>> print a['klim']
300
>>> 
klim@moose:~> cat sum-vars.py
#!/usr/bin/python

import sys

sum = {}                        <--- initialze the dictionary

for l in sys.stdin.readlines(): <--- for each line read from stdin
  if l[0] == '#':  continue     <--- skip a comment line

  fs = l[:-1].split()           <--- remove \n and split the line into fields
  if fs[0] not in sum:          <--- if key not present
    sum[fs[0]] = 0              <---    add a new pair
  for n in  fs[1:] :            <--- for other fields (i.e numbers) in line
    sum[fs[0]] +=  int(n)       <---    summing

for k in sum.keys():
  print k, sum[k]

klim@moose:~> cat IN-num
klim 233   112 33               <----- input data begins
# oh!, just a test              <--    comment
# again                         <--    comment
milk 333  22                    <--
klim 999 22                     <--
oak 222                         <--
redcow 1023                     <--
oak 11                          <----- input data ends here
klim@moose:~/demo-awk> python sum-vars.py < IN-num
redcow 1023                     <------ the answer is ......
klim 1399
oak 233
milk 355
klim@moose:~>