Utility functions

>>> from __future__ import print_function
>>> from nltk.util import *
>>> from nltk.tree import Tree

>>> print_string("This is a long string, therefore it should break", 25)
This is a long string,
therefore it should break

>>> re_show("[a-z]+", "sdf123")
{sdf}123

>>> tree = Tree(5,
...             [Tree(4, [Tree(2, [1, 3])]),
...              Tree(8, [Tree(6, [7]), 9])])
>>> for x in breadth_first(tree):
...     if isinstance(x, int): print(x)
...     else: print(x.label())
5
4
8
2
6
9
1
3
7
>>> for x in breadth_first(tree, maxdepth=2):
...     if isinstance(x, int): print(x)
...     else: print(x.label())
5
4
8
2
6
9

>>> invert_dict({1: 2})
defaultdict(<... 'list'>, {2: 1})

>>> invert_dict({1: [3, 4, 5]})
defaultdict(<... 'list'>, {3: [1], 4: [1], 5: [1]})