combining one-column text files into one multi-column file, separated by tabs

Question

I have several one-column text files that I want to put next to each other (e.g. each file is one column). The only documentation I could find was on appending files to the bott

Answer 1

Here's a good way to do it incrementally and makes sure all the files involved are closed when it ends:

from contextlib import contextmanager
import glob
from itertools import izip

@contextmanager
def multi_file_manager(files, mode='rb'):
    """ Open multiple files and make sure they all get closed. """
    files = [open(file, mode) for file in files]
    yield files
    for file in files:
        file.close()

def read_info(file):
    """ Generator function to read and extract info from each line of a file. """
    for line in file:
        yield line.split('[')[0]

with open("MA_continuous_results.csv", "wb") as outfile:
    MA_files = glob.glob("MA*continuous*2")

    col_headers = (filename.split("maskave_")[-1] for filename in MA_files)
    outfile.write('\t'.join(col_headers) + '\n')

    with multi_file_manager(MA_files) as infiles:
        generators = [read_info(file) for file in infiles]

        for fields in izip(*generators):
            outfile.write('\t'.join(fields) + '\n')

Answer 2

I would rewrite your code as follows:

import glob
from itertools import izip

def extract_meaningful_info(line):
    return line.rstrip('\n').split('[')[0]

MA_files = glob.glob("MA*continuous*2")

with open("MA_continuous_results.csv", "wb") as outfile:
    outfile.write("\t".join(MA_files) + '\n')
    for fields in izip(*(open(f) for f in MA_files)):
        fields = [extract_meaningful_info(f) for f in fields]
        outfile.write('\t'.join(fields) + '\n')

(code is for python2)

You might want to read about:

• itertools.izip

• * in the arguments of function