I want to compare two CSV files with the following format. They not have headers. I want to compare them by a specific column (in this case, the 2nd one).
The source CSV files around 4-5GB, so loading them into memory is won't work.
If there's no matching column in old.csv, than every new line written into out.csv.
This 2nd column will be a html link, for the shake of simplicity, here one word only.
My question is it possible to achieve the same result with sed, awk, join, or grep?
old.csv
"person"|"john"|"smith"
"person"|"anne"|"frank"
"person"|"bob"|"macdonald"
"fruit"|"orange"|"banana"
"fruit"|"strawberry"|"fields"
"fruit"|"ringring"|"banana"
new.csv
"person"|"john"|"smith"
"person"|"anne"|"frank"
"person"|"bob"|"macdonald"
"fruit"|"orange"|"banana"
"fruit"|"strawberry"|"fields"
"glider"|"person"|"airport"
"fruit"|"ringring"|"banana"
"glider"|"person2"|"airport"
diff.py
#!/usr/bin/env python3
"""
Source: https://gist.github.com/davidrleonard/4dbeebf749248a956e44
Usage: $ ./csv-difference.py -d new.csv -s old.csv -o out.csv -c 1
"""
import sys
import argparse
import csv
def main():
parser = argparse.ArgumentParser(description='Output difference in CSVs.')
parser.add_argument('-d', '--dataset', help='A CSV file of the full dataset', required=True)
parser.add_argument('-s', '--subset', help='A CSV file that is a subset of the full dataset', required=True)
parser.add_argument('-o', '--output', help='The CSV file we should write to (will be overwritten if it exists', required=True)
parser.add_argument('-c', '--column', help='A number of the column to be compared (0 is column 1, 1 is column 2, etc.)', required=True, type=int)
args = parser.parse_args()
dataset_file = args.dataset
subset_file = args.subset
output_file = args.output
column_num = args.column
with open(dataset_file, 'r') as datafile, open(subset_file, 'r') as subsetfile, open(output_file, 'w') as outputfile:
data = {row[column_num]: row for row in csv.reader(datafile, delimiter='|', quotechar='"')}
subset = {row[column_num]: row for row in csv.reader(subsetfile, delimiter='|', quotechar='"')}
data_keys = set(data.keys())
subset_keys = set(subset.keys())
output_keys = data_keys - subset_keys
output = [data[key] for key in output_keys]
output_csv = csv.writer(outputfile, delimiter='|', quotechar='"', quoting=csv.QUOTE_ALL)
for row in output:
output_csv.writerow(row)
if __name__ == '__main__':
main()
sys.stdout.flush()
Which is generating out.csv
"glider"|"person"|"airport"
"glider"|"person2"|"airport"
output_keys
should simply bedata.keys() - subset.keys()
. Or, even better,output = {v for k, v in data.items() if k not in subset}
– iruvar Nov 4 '16 at 22:20