CODEWITHSUNDEEP
python
user3224522
user3224522

Reputation: 1151

Get an element with the highest value in python

If my tab-delimited file is:

a b 77.8
a d 77.8
e f 56.7
e r 40.0

I want to print an elem in line[0] with max value in line[2], but when the value is the same, to print both, how to modify my code below for this?

import csv
from itertools import groupby
from operator import itemgetter
with open('input.txt,'rb') as f1:
    with open('out.txt','wb') as f2:
        reader = csv.reader(f1, delimiter='\t')
        writer1 = csv.writer(f2, delimiter='\t')
        for group, rows in groupby(filter(lambda x: x[0]!=x[1], reader), key=itemgetter(0)):
            best = max(rows, key=lambda r: (float(r[2])))
            writer1.writerow(best)

So, my output should be like this:

 a b 77.8
 a d 77.8
 e f 56.7

Upvotes: 0

Views: 102

Answers (2)

oliversm
oliversm

Reputation: 1967

An alternative which uses pandas, (where the reading and writing to files is nicer):

import pandas as pd

df = pd.read_table('eg.txt', header=None, sep=' ')

with open('output.txt', 'wb') as f:
    for c in set(df[0]):
        d = df[df[0] == c].sort_values(by=[2], ascending=False)
        d = d[d[2] == d[2].iloc[0]]
        d.to_csv(f, index=False, sep='\t', header=False)

which gives output:

a   b   77.8
a   d   77.8
e   f   56.7

Upvotes: 1

niemmi
niemmi

Reputation: 17263

Instead of writing the max item from rows you could sort the row in decreasing order by third value, group it by third value and write the items in first group:

import csv
from itertools import groupby
from operator import itemgetter

with open('input.txt','rb') as f_in, open('out.txt','wb') as f_out:
    reader = csv.reader(f_in, delimiter='\t')
    writer1 = csv.writer(f_out, delimiter='\t')
    for group, rows in groupby(filter(lambda x: x[0]!=x[1], reader), key=itemgetter(0)):
        rows = sorted(rows, key=lambda r: (float(r[2])), reverse=True)
        _, best = next(groupby(rows, key=itemgetter(2)))
        writer1.writerows(best)

Output in out.txt:

a   b   77.8
a   d   77.8
e   f   56.7

Upvotes: 1

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