I am currently trying to count repeated values in a column of a CSV file and return the value to another CSV column in a python.

For example, my CSV file :

KeyID    GeneralID
145258   KL456
145259   BG486
145260   HJ789
145261   KL456

What I want to achieve is to count how many data have the same GeneralID and insert it into a new CSV column. For example,

KeyID    Total_GeneralID
145258   2
145259   1
145260   1
145261   2

I have tried to split each column using the split method but it didn't work so well.

My code :

case_id_list_data = []

with open(file_path_1, "rU") as g:
    for line in g:
        case_id_list_data.append(line.split('\t'))
        #print case_id_list_data[0][0] #the result is dissatisfying
        #I'm stuck here..

And if you are adverse to pandas and want to stay with the standard library:

Code:

import csv
from collections import Counter
with open('file1', 'rU') as f:
    reader = csv.reader(f, delimiter='\t')
    header = next(reader)
    lines = [line for line in reader]
    counts = Counter([l[1] for l in lines])

new_lines = [l + [str(counts[l[1]])] for l in lines]
with open('file2', 'wb') as f:
    writer = csv.writer(f, delimiter='\t')
    writer.writerow(header + ['Total_GeneralID'])
    writer.writerows(new_lines)

Results:

KeyID   GeneralID   Total_GeneralID
145258  KL456   2
145259  BG486   1
145260  HJ789   1
145261  KL456   2

more