Question

I am writing a code which compares file1 (single column of entries) with file 2 (3 column of entries) and fetch matched records from file 2 on basis of first column. The problem is that it is evaluating the loop only once.

File1:

ABC

DEF

JKL

File2:

IJK,123,SDF

ABC,456,HJK

QWE,876,GFT

JKL,098,HGF

…..

My code:

for entry in fh_file1:
    mir = entry.strip('\n')
    print(mir)
    for row in fh_file2:
        row_splt = row.split(',')             
        print(row_splt[0])
        if mir in row_splt[0]:
            print (row.strip('\n'))
        else:
            pass

Result from that code:

is just the match of first entry of file 1:

ABC 456 HJK

Please help me on this.

Answer 1

You need to add fh_file2.seek(0) before the second for loop to start over at the beginning of the file.

You’d be better served, however, by reading it into memory once:

file2_lines = fh.file2.readlines()

then iterating over file2_lines. Reading the file from disk for each line in another file is going to be very slow.