>>> from nltk.corpora import cmudict
    >>> from string import join
    >>> for word, num, pron in cmudict.raw():
    ...     stress_pattern = join(c for c in join(pron) if c in "012")
    ...     if stress_pattern.endswith("1 0 0 0 0"):
    ...         print word, "/", join(pron)




    >>> from nltk.corpora import shoebox
    >>> from nltk.utilities import MinimalSet
    >>> length, position, min = 4, 1, 3
    >>> lexemes = [field[1].lower() for entry in shoebox.raw('rotokas.dic')
    ...		   for field in entry if field[0] == 'lx']
    >>> ms = MinimalSet()
    >>> for lex in lexemes:
    ...     if len(lex) == length:
    ...         context = lex[:position] + '_' + lex[position+1:]
    ...         target = lex[position]
    ...         ms.add(context, target, lex)
    >>> for context in ms.contexts(3):
    ...     for target in ms.targets():
    ...         print "%-4s" % ms.display(context, target, "-"),
    ...     print



    >>> from nltk.corpora import genesis
    >>> from nltk.probability import ConditionalFreqDist
    >>> from nltk.utilities import print_string
    >>> cfdist = ConditionalFreqDist()
    >>> prev = None
    >>> for word in genesis.raw():
    ...     word = word.lower()
    ...     cfdist[prev].inc(word)
    ...     prev = word
    >>> words = []
    >>> prev = 'lo,'
    >>> for i in range(99):
    ...     words.append(prev)
    ...     for word in cfdist[prev].sorted():
    ...         if word not in words:
    ...             break
    ...     prev = word
    >>> print_string(join(words))





    >>> from nltk.corpora import treebank
    >>> from string import join
    >>> def vp_conj(tree):
    ...     if tree.node == 'VP' and len(tree) == 3 and tree[1].leaves() == ['but']:
    ...         return True
    ...     else:
    ...         return False
    >>> for tree in treebank.parsed_sents():
    ...     for vp1,conj,vp2 in tree.subtrees(vp_conj):
    ...         print join(child.node for child in vp1), "*BUT*", join(child.node for child in vp2)



from nltk.corpora import treebank
from string import join
def vp_conj(tree):
    if tree.node == 'VP' and len(tree) == 3 and tree[1].leaves() == ['but']:
        return True
    else:
        return False

def pr(subtree):
    return "(%s %s)" % (subtree.node, join(subtree.leaves()))

for tree in treebank.parsed_sents():
    for vp1,conj,vp2 in tree.subtrees(vp_conj):
        print join(pr(child) for child in vp1), "*BUT*", join(pr(child) for child in vp2)