file read and for loop in python

Question

I have this file:

and I want to sort them and store them to a file.

I read the file store them inside a list , sort the list and then save the list to a file. Problem is that It starts from the second -x .

 for line in file:
        temp_buffer = line.split()
        for i,word in enumerate(temp_buffer):
            if "-" not in word:
                if word in index_dict:
                    l1.append(word)
                else:
                    l1.append(function(word))
            else:
                l1.append(word)
                l1.sort()
                print(l1 , file=testfile)
                del l1
                l1 = []

So the 1st loop it goes to the else statment and stores just the first -0 without the words beween -0 and -00. How should I fix this ? I want the output to be like that :

DSM · Accepted Answer · 2014-03-05 19:34:27Z

7

You can use itertools.groupby to "partition" the data into groups between lines starting with - instead. Where it starts with - write the line out, otherwise, write the sorted lines, eg:

from itertools import groupby

with open('input') as fin, open('output', 'w') as fout:
  for k, g in groupby(fin, lambda L: L.startswith('-')):
    if k:
      fout.writelines(g)
    else:
      fout.writelines(sorted(g, key=int))

edited Mar 5, 2014 at 19:34

DSM

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answered Mar 5, 2014 at 19:29

Jon Clements

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4 Comments

bill Over a year ago

will this sort the list in every loop ? because i need to keep the complexity low.

Jon Clements Over a year ago

It will sort the items between each line starting with -

bill Over a year ago

input file is huge so i need to group the elements and when the group is full(all the elements between -x -xxxx) then store it to the file. will this function try to read all the file and try to group it and then store it ?

Jon Clements Over a year ago

@Bill no... it will consume and sort the parts between the -'s as it goes... It will only have in memory the lines between a single set of markers at any one time

Archit Jain · Accepted Answer · 2014-03-05 19:33:38Z

0

You may use this :

l1=[]
for i,word in enumerate(temp_buffer):
            if "-" in word:
                l1.sort()
                print(l1)
                l1 = []
            if word in index_dict:
                l1.append(word)
            else:
                l1.append(function(word))

answered Mar 5, 2014 at 19:33

Archit Jain

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