Draw nested ascii tables in Python

nested_table.py

from StringIO import StringIO
from operator import attrgetter
import textwrap

class Node(object):
    def __init__(self, val=None, *children):
        self.val = val
        self.children = list(children)

test1 = Node("foo")
test2 = Node("foo", Node("bar"))
test3 = Node("foo", Node("spam", Node("spam1"), Node("spam2")),
                    Node("eggs", Node("eggs1"), Node("eggs2")))

test4 = Node("", Node("", Node("", Node("", Node("", Node(("suck it", "you", "bitch")))))))


def draw_nested(tree, valfn=attrgetter("val"), childfn=attrgetter("children"), maxwidth=0):
    def _draw_table(root, prefix, acc):
        val, children = valfn(root), childfn(root)
        acc.append((prefix+".", "", "-", False))
        if isinstance(val, (list, tuple)):
            for val in val:
                acc.append((prefix + "| ", val, " ", True))
        elif val:
            acc.append((prefix+ "| ", val, " ", True))
        for child in children:
            _draw_table(child, prefix + "| ", acc)
        acc.append((prefix+"'", "", "-", False))
        return acc
    
    table = _draw_table(tree, "", [])
    buff = StringIO()
    if maxwidth <= 0:
        maxwidth = max(2 * len(prefix) + len(text) for prefix, text, _, _ in table)
    
    for prefix, text, fill, is_content in table:
        if is_content:
            contentwidth = maxwidth - 2 * len(prefix)
            lines = textwrap.wrap(text, width=contentwidth)
        else:
            lines = [text]
        for line in lines:
            fillwidth = maxwidth - 2 * len(prefix) - len(line)
            buff.write("{}{}{}{}\n".format(
                prefix, line.encode("utf-8"), fill * fillwidth, prefix[::-1]))
        
    return buff.getvalue()

lines = draw_nested(test4)
print lines

output.txt

.---------------. 
| foo           | 
| .-----------. | 
| | spam      | | 
| | .-------. | | 
| | | spam1 | | | 
| | '-------' | | 
| | .-------. | | 
| | | spam2 | | | 
| | '-------' | | 
| '-----------' | 
| .-----------. | 
| | eggs      | | 
| | .-------. | | 
| | | eggs1 | | | 
| | '-------' | | 
| | .-------. | | 
| | | eggs2 | | | 
| | '-------' | | 
| '-----------' | 
'---------------'

Reddit comment example:

.-------------------------------------------. 
| .---------------------------------------. | 
| | ingolemo (2/0)                        | | 
| | Looks to me like it would be better   | | 
| | to split at the commas and then strip | | 
| | off the whitespace. Either way, this  | | 
| | would be best accomplished with a     | | 
| | list comprehesion;      for line in   | | 
| | gradefile:         linelist =         | | 
| | [field.strip() for field in           | | 
| | line.split(',')]         # do         | | 
| | something with linelist               | | 
| | .-----------------------------------. | | 
| | | Blackshirt12 (1/0)                | | | 
| | | So what is a field in this        | | | 
| | | context? This worked for me, but  | | | 
| | | I don't understand why. I haven't | | | 
| | | used this method before.          | | | 
| | | .-------------------------------. | | | 
| | | | ingolemo (1/0)                | | | | 
| | | | It's just the name that I     | | | | 
| | | | gave to the variable that     | | | | 
| | | | temporarily holds each of the | | | | 
| | | | sub-items in                  | | | | 
| | | | `line.split(',')`. it's       | | | | 
| | | | analogous to `line` on the    | | | | 
| | | | line above it.                | | | | 
| | | | .---------------------------. | | | | 
| | | | | zahlman (1/0)             | | | | | 
| | | | | I don't know why you were | | | | | 
| | | | | downvoted. This is        | | | | | 
| | | | | exactly how I'd do it and | | | | | 
| | | | | it's perfectly idiomatic  | | | | | 
| | | | | and correct.              | | | | | 
| | | | '---------------------------' | | | | 
| | | '-------------------------------' | | | 
| | '-----------------------------------' | | 
| '---------------------------------------' | 
| .---------------------------------------. | 
| | ahnakel (1/0)                         | | 
| | Do you just need to remove the last   | | 
| | character? linelist[:-1] should       | | 
| | reference all elements in a list      | | 
| | before the last one.                  | | 
| '---------------------------------------' | 
| .---------------------------------------. | 
| | pkkid (1/0)                           | | 
| | Assuming `gradefile` is a list of 4   | | 
| | strings as you suggest in your        | | 
| | description, something like the       | | 
| | following should work:      # Remove  | | 
| | trailing commas     gradefile =       | | 
| | [x.rstrip(",") for x in gradefile]    | | 
| | # Convert one of them to a float      | | 
| | gradefile[3] = float(gradefile[3])    | | 
| '---------------------------------------' | 
'-------------------------------------------'