How to print a list more nicely?

Question

This is similar to How to print a list in Python “nicely”, but I would like to print the list even more nicely -- without the brackets and apostrophes and commas, and even b

Answer 1

It's useful to allow for uneven columns, without having to know in advance how many columns you can fit:

>>> words = [string.ascii_lowercase] + list(string.ascii_lowercase)
>>> print format_list(words)
abcdefghijklmnopqrstuvwxyz  b  d  f  h  j  l  n  p  r  t  v  x  z
a                           c  e  g  i  k  m  o  q  s  u  w  y

For your example:

>>> foolist = ['exiv2-devel', 'mingw-libs', 'tcltk-demos', 'fcgi',
... 'netcdf', 'pdcurses-devel', 'msvcrt', 'gdal-grass', 'iconv',
... 'qgis-devel', 'qgis1.1', 'php_mapscript']
>>> print format_list(foolist, spacing=4, width=31)
exiv2-devel       msvcrt
mingw-libs        gdal-grass
tcltk-demos       iconv
fcgi              qgis-devel
netcdf            qgis1.1
pdcurses-devel    php_mapscript

Here is the code. Note that it also handles words with ANSI color codes (such as from the colorama package) - they won't mess up the column widths.

ansi_pattern = re.compile(r'\x1b\[\d{1,2}m')


def get_nchars(string):
    """Return number of characters, omitting ANSI codes."""
    return len(ansi_pattern.sub('', string))


def format_list(items, indent=0, spacing=2, width=79):
    """Return string listing items along columns.

    items : sequence
        List of items to display that must be directly convertible into
        unicode strings. ANSI color codes may be present, and are taken
        into account in determining column widths
    indent : int
        Number of spaces in left margin.
    spacing : int
        Number of spaces between columns.
    width : int
        Maximum number of characters per line, including indentation.
    """
    if not items:
        return u''
    # Ensure all items are strings
    items = [unicode(item) for item in items]
    # Estimate number of columns based on shortest and longest items
    minlen = min(get_nchars(item) for item in items)
    maxlen = max(get_nchars(item) for item in items)
    # Assume one column with longest width, remaining with shortest.
    # Use negative numbers for ceiling division.
    ncols = 1 - (-(width - indent - maxlen) // (spacing + min(1, minlen)))
    ncols = max(1, min(len(items), ncols))

    # Reduce number of columns until items fit (or only one column)
    while ncols >= 1:
        # Determine number of rows by ceiling division
        nrows = -(-len(items) // ncols)
        # Readjust to avoid empty last column
        ncols = -(-len(items) // nrows)
        # Split items into columns, and test width
        columns = [items[i*nrows:(i+1)*nrows] for i in range(ncols)]
        totalwidth = indent - spacing + sum(
            spacing + max(get_nchars(item) for item in column)
            for column in columns
            )
        # Stop if columns fit. Otherwise, reduce number of columns and
        # try again.
        if totalwidth <= width:
            break
        else:
            ncols -= 1

    # Pad all items to column width
    for i, column in enumerate(columns):
        colwidth = max(get_nchars(item) for item in column)
        columns[i] = [
            item + ' ' * (colwidth - get_nchars(item))
            for item in column
            ]

    # Transpose into rows, and return joined rows
    rows = list(itertools.izip_longest(*columns, fillvalue=''))
    return '\n'.join(
        ' ' * indent + (u' ' * spacing).join(row).rstrip()
        for row in rows
        )