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#!/usr/bin/env python
# Usage: extract-target-trees.py [FILE]
#
# Reads moses-chart's -T output from FILE or standard input and writes trees to
# standard output in Moses' XML tree format.
import re
import sys
class Tree:
def __init__(self, label, children):
self.label = label
self.children = children
def is_leaf(self):
return len(self.children) == 0
class Derivation(list):
def find_root(self):
assert len(self) > 0
root = None
for hypothesis in self:
if hypothesis.span[0] != 0:
continue
if root == None or hypothesis.span[1] > root.span[1]:
root = hypothesis
assert root
return root
def construct_target_tree(self):
hypo_map = {}
for hypothesis in self:
hypo_map[hypothesis.span] = hypothesis
root = self.find_root()
return self._build_tree(root, hypo_map)
def _build_tree(self, root, hypo_map):
def escape_label(label):
s = label.replace("&", "&")
s = s.replace("<", "<")
s = s.replace(">", ">")
return s
# Build list of NT spans in source order...
non_term_spans = []
for item in root.source_symbol_info:
span = item[0]
if span != root.span and span in hypo_map: # In hypo_map iff symbol is NT
non_term_spans.append(span)
non_term_spans.sort()
# ... then convert to target order.
alignment_pairs = root.nt_alignments[:]
alignment_pairs.sort()
target_order_non_term_spans = {}
for i, pair in enumerate(alignment_pairs):
target_order_non_term_spans[pair[1]] = non_term_spans[i]
children = []
num_non_terms = 0
for i, symbol in enumerate(root.target_rhs):
if i in target_order_non_term_spans:
hyp = hypo_map[target_order_non_term_spans[i]]
children.append(self._build_tree(hyp, hypo_map))
num_non_terms += 1
else:
children.append(Tree(escape_label(symbol), []))
assert num_non_terms == len(root.nt_alignments)
return Tree(root.target_lhs, children)
class Hypothesis:
def __init__(self):
self.sentence_num = None
self.span = None
self.source_symbol_info = None
self.target_lhs = None
self.target_rhs = None
self.nt_alignments = None
def read_derivations(input):
line_num = 0
start_line_num = None
prev_sentence_num = None
derivation = Derivation()
for line in input:
line_num += 1
hypothesis = parse_line(line)
if hypothesis.sentence_num != prev_sentence_num:
# We've started reading the next derivation...
prev_sentence_num = hypothesis.sentence_num
if len(derivation):
yield derivation, start_line_num
derivation = Derivation()
start_line_num = line_num
derivation.append(hypothesis)
if len(derivation):
yield derivation, start_line_num
# Extract the hypothesis components and return a Hypothesis object.
def parse_line(s):
pattern = r"Trans Opt (\d+) " + \
r"\[(\d+)\.\.(\d+)\]:" + \
r"((?: \[\d+\.\.\d+\]=\S+ )+):" + \
r" (\S+) ->" + \
r"((?:\S+ )+):" + \
r"((?:\d+-\d+ )*): pC="
regexp = re.compile(pattern)
match = regexp.match(s)
if not match:
sys.stderr.write("%s\n" % s)
assert match
group = match.groups()
hypothesis = Hypothesis()
hypothesis.sentence_num = int(group[0]) + 1
hypothesis.span = (int(group[1]), int(group[2]))
hypothesis.source_symbol_info = []
for item in group[3].split():
pattern = "\[(\d+)\.\.(\d+)\]=(\S+)"
regexp = re.compile(pattern)
match = regexp.match(item)
assert(match)
start, end, symbol = match.groups()
span = (int(start), int(end))
hypothesis.source_symbol_info.append((span, symbol))
hypothesis.target_lhs = group[4]
hypothesis.target_rhs = group[5].split()
hypothesis.nt_alignments = []
for pair in group[6].split():
match = re.match(r'(\d+)-(\d+)', pair)
assert match
ai = (int(match.group(1)), int(match.group(2)))
hypothesis.nt_alignments.append(ai)
return hypothesis
def tree_to_xml(tree):
if tree.is_leaf():
return tree.label
else:
s = '<tree label="%s"> ' % tree.label
for child in tree.children:
s += tree_to_xml(child)
s += " "
s += '</tree>'
return s
def main():
if len(sys.argv) > 2:
sys.stderr.write("usage: %s [FILE]\n" % sys.argv[0])
sys.exit(1)
if len(sys.argv) == 1 or sys.argv[1] == "-":
input = sys.stdin
else:
input = open(sys.argv[1])
for derivation, line_num in read_derivations(input):
try:
tree = derivation.construct_target_tree()
except:
msg = "error processing derivation starting at line %d\n" % line_num
sys.stderr.write(msg)
raise
print tree_to_xml(tree)
if __name__ == '__main__':
main()
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