Commandline script to center text

centerer.py

#!/usr/bin/env python3
"""Commandline script to center text horizontally."""
import argparse


def center(line: str, width: int, length: int = None):
    """Center a line within a width, optionally treating it as len length.

    >>> center('foo', 6)
    ' foo'
    >>> center('fo', 6)
    '  fo'
    >>> center('foo', 3)
    'foo'

    >>> center('foo', 6, length=4)
    ' foo'
    >>> center('foo', 9, length=5)
    '  foo'
    """
    return ' '*((width - (len(line) if length is None else length)) // 2) + line


def fill(line: str, width: int):
    """Fill a line with trailing whitespace to width.

    >>> fill('foo', 6)
    'foo   '
    >>> fill('foo', 3)
    'foo'
    >>> fill('foo', 2)
    'foo'
    """
    return line + ' '*(width-len(line))


if __name__ == '__main__':
    parser = argparse.ArgumentParser(description='Center text horizontally e.g. "foo" -> " foo "')
    parser.add_argument('infile', type=argparse.FileType('r'),
                        help='Input file (use `-` for stdin).')
    parser.add_argument('-w', '--width', type=int, default=80,
                        help='Width to center within (default: 80).')
    parser.add_argument('-v', '--vertical', type=int, help='Center vertically for the given height in lines.')
    parser.add_argument('-f', '--fill', action='store_true', help='Add trailing lines and spaces.')
    parser.add_argument('--line', action='store_true', help='Center on a line-by-line basis, instead of the longest line in the file.')
    args = parser.parse_args()

    lines = [line.strip('\n') for line in args.infile.readlines()]

    lens = [len(line) for line in lines]
    max_len = max(lens)

    lines = list(map(lambda l: center(l, width=args.width, length=(None if args.line else max_len)), lines))

    if args.vertical is not None:
        lines = (['']*((args.vertical - len(lines)) // 2)) + lines

    if args.fill:
        if args.vertical is not None:
            lines.extend(['']*(args.vertical - len(lines)))
        lines = list(map(lambda l: fill(l, width=args.width), lines))

    [print(line) for line in lines]  # spit back out