Parsing, Aggregating & Sorting text file in Python

Question

I have the file named "names.txt" having the following contents:

{"1":[1988, "Anil 4"], "2":[2000, "Chris 4"], "3":[1988, "Rahul 1"],
"4":[2001, "Kechit 3"], "5":[2000, "Phil 3"], "6":[2001, "Ravi 4"],
"7":[1988, "Ramu 3"], "8":[1988, "Raheem 5"], "9":[1988, "Kranti 2"],
"10":[2000, "Wayne 1"], "11":[2000, "Javier 2"], "12":[2000, "Juan 2"],
"13":[2001, "Gaston 2"], "14":[2001, "Diego 5"], "15":[2001, "Fernando 1"]}

Problem statement : File "names.txt" contains some student records in the format -

{"number": [year of birth, "name rank"]}

Parse this file and Segregate them according to year and then sort the names according to rank. First segregation and then sorting. Output should be in the format -

{year : [Names of students in sorted order according to rank]}

So the expected output is -

{1988:["Rahul 1","Kranti 2","Rama 3","Anil 4","Raheem 5"],
2000:["Wayne 1","Javier 2","Jaan 2","Phil 3","Chris 4"],
2001:["Fernando 1","Gaston 2","Kechit 3","Ravi 4","Diego 5"]}

First How to store this file content in a dictionary object? Then Grouping by year & then ordering names by rank? How to achieve this in Python?

Thanks..

Sounds suspiciously like homework. But to lend a hand, I would suggest looking into the `json` module, which will read that content in to python, then you can modify it as a python dictionary, then you can output it again to a file in `json` — CasualDemon, Aug 21 '15 at 16:55
Then convert this list to a dictionary, maybe dict.fromkeys() might help, or you can arrange your own function/code. However I recommend to have a look on json either in python 2 or python 3. — llrs, Aug 21 '15 at 17:13
No way the +7 upvotes for a "do my homework question" are legit. — Chris Seymour, Aug 23 '15 at 15:39
@iiSeymour It's from classmates, eager to see this answered too, I guess. :-) — BlackJack, Aug 24 '15 at 16:37

score 1 · Accepted Answer · answered Oct 14 '15 at 09:10

Its Very Simple :)

#!/usr/bin/python
# Program: Parsing, Aggregating & Sorting text file in Python
# Developed By: Pratik Patil
# Date: 22-08-2015

import pprint;

# Open file & store the contents in a dictionary object
file = open("names.txt","r");
file_contents=eval(file.readlines().pop(0));

# Extract all lists from file contents
file_contents_values=file_contents.values();

# Extract Unique Years & apply segregation
year=sorted(set(map(lambda x:x[0], file_contents_values)));
file_contents_values_grouped_by_year = [ [y[1] for y in file_contents_values if y[0]==x ] for x in year];

# Create Final Dictionary by combining respective keys & values
output=dict(zip(year, file_contents_values_grouped_by_year));

# Apply Sorting based on ranking
for NameRank in output.values():
    NameRank.sort(key=lambda x: int(x.split()[1]));

# Print Output by ascending order of keys
pprint.pprint(output);

score -1 · Answer 2 · answered Aug 22 '15 at 12:35

The segregation can be done with a collections.defaultdict in a simple loop. Then another loop over the students lists to sort them according to the integer value of the last part of the student entries. And pprint() prints the desired ouput if we convert the defaultdict into a regular one:

#!/usr/bin/env python
from __future__ import absolute_import, division, print_function
import json
from collections import defaultdict
from pprint import pprint


def main():
    with open('test.json') as student_file:
        id2student = json.load(student_file)
    # 
    # Segregate by year.
    # 
    year2students = defaultdict(list)
    for year, student_and_rank in id2student.itervalues():
        year2students[year].append(student_and_rank.encode('utf8'))
    # 
    # Sort by rank.
    # 
    for students in year2students.itervalues():
        students.sort(key=lambda s: int(s.rsplit(' ', 1)[-1]))

    pprint(dict(year2students))


if __name__ == '__main__':
    main()

Parsing, Aggregating & Sorting text file in Python

2 Answers2