Pretty-print multiple levels of nested braces

bracefilter.py

#!/usr/bin/env python3

import sys


linechar = '\x1b[92m|\x1b[0m' if sys.stdout.isatty() else '|'


def indent(nest):
    sys.stdout.write('{}   '.format(linechar) * nest)


def main():
    s = sys.stdin.read()
    nest = 0
    comma = False
    for c in s:
        if c != ' ':
            if comma:
                comma = False
                sys.stdout.write('\n')
                indent(nest)

        if c in '[({<':
            sys.stdout.write(c + '\n')
            nest += 1
            indent(nest)
        elif c in '])}>':
            sys.stdout.write('\n')
            nest -= 1
            indent(nest)
            sys.stdout.write(c)
        elif c == ',':
            comma = True
            sys.stdout.write(',')
        elif c != ' ':
            sys.stdout.write(c)
        elif c == ' ':
            if not comma or nest <= 0:
                sys.stdout.write(c)


if __name__ == '__main__':
    main()

usage.txt

$ cat test.txt 
foo: {bar, (baz, abc, def, d[a, b, ccc]), [13, 24, f(24)]}
$ bracefilter < test.txt 
foo: {
|   bar,
|   (
|   |   baz,
|   |   abc,
|   |   def,
|   |   d[
|   |   |   a,
|   |   |   b,
|   |   |   ccc
|   |   ]
|   ),
|   [
|   |   13,
|   |   24,
|   |   f(
|   |   |   24
|   |   )
|   ]
}