interleave

#!/usr/bin/env python
#
#######################################################################
#
#
#   interleave
#
#   USAGE: ./interleave [--no-break] file1 file2 [...]
#
#   Interleave files to stdout.
#
#   Output will be of the following form:
#    line 1 of file 1
#    line 1 of file 2
#    ...
#
#    line 2 of file 1
#    line 2 of file 2
#       ...
#
#   At least two files must be given as command-line parameters.
#   If the --no-break option is given, then no linebreak is inserted
#   between the each set of lines.
#
#   TODO
#       * Low-memory mode, which doesn't read in the files all at once.
#
#
#######################################################################

import sys, string

args = sys.argv[1:]
no_break = False
if args[0] == "--no-break":
    no_break = True
    args = args[1:]

# The number of files to be interleaved
cnt = len(args)
assert cnt >= 2

from common.file import myopen
lines = []
for n in args:
#    sys.stderr.write("%s\n" % n)
    if n == "-":
        f = sys.stdin
    else:
        f = myopen(n)
    lines.append(f.readlines())
    f.close()

# Make sure all files have the same number of lines
for i in range(1, cnt):
    assert len(lines[i]) == len(lines[0])

# Now, actually interleave them
for i1 in range(len(lines[0])):
    for i2 in range(cnt):
        print string.strip(lines[i2][i1]),
        if not no_break: print
    if no_break: print