csvmerge

#!/usr/bin/python3

# This script is also dedicated to Brandon.

from itertools import zip_longest
from sys import argv

def firstcol(string, delim):
	if string == None:
		return float('inf')
	return int(string.split(delim)[0])

def restcols(string, delim):
	if string == None:
		return 0
	return string[string.index(delim) + 1:].strip()

def main():
	if len(argv) <= 2:
		print("USAGE: {} <delimiter> <files>...".format(argv[0]))
		exit(1)

	delim = argv[1]
	numfiles = len(argv) - 2
	fds = [open(fn) for fn in argv[2:]]

	numdelims = None
	for fd in fds:
		curheader = next(fd)
		curnumdelims = curheader.count(delim)
		if numdelims == None:
			print(curheader.strip(), end='')
			for time in range(numfiles - 1):
				print(delim, end='')
				print(restcols(curheader, delim), end='')
			print()
			numdelims = curnumdelims
			continue
		if curnumdelims != numdelims:
			print('Error: CSVs have different numbers of columns or delimiters')
			return
	placeholder = delim * numdelims

	nextel = [next(fd) for fd in fds]

	while nextel.count(None) != len(fds):
		maxel = firstcol(min(nextel, key = lambda x: firstcol(x, delim)), delim)
		res = str(maxel)
		for idx in range(len(nextel)):
			if firstcol(nextel[idx], delim) == maxel:
				res += delim + restcols(nextel[idx], delim)
				nextel[idx] = next(fds[idx], None)
			else:
				res += placeholder
		print(res)

	for fd in fds:
		fd.close()

if __name__ == '__main__':
	main()