How to use the pynini.union function in pynini
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kylebgorman / EditTransducer / edit_transducer / edit_transducer.py View on Github 
def __init__(self,
alphabet,
insert_cost=DEFAULT_INSERT_COST,
delete_cost=DEFAULT_DELETE_COST,
substitute_cost=DEFAULT_SUBSTITUTE_COST):
"""Constructor.
Args:
alphabet: edit alphabet (an iterable of strings).
insert_cost: the cost for the insertion operation.
delete_cost: the cost for the deletion operation.
substitute_cost: the cost for the substitution operation.
"""
# Left factor; note that we divide the edit costs by two because they also
# will be incurred when traversing the right factor.
match = union(*alphabet).optimize(True)
i_insert = transducer("", "[{}]".format(self.INSERT),
weight=insert_cost / 2).optimize(True)
i_delete = transducer(match, "[{}]".format(self.DELETE),
weight=delete_cost / 2).optimize(True)
i_substitute = transducer(match, "[{}]".format(self.SUBSTITUTE),
weight=substitute_cost / 2).optimize(True)
i_ops = union(match, i_insert, i_delete, i_substitute).optimize(True)
# Right factor; this is constructed by inverting the left factor (i.e.,
# swapping the input and output labels), then swapping the insert and delete
# labels on what is now the input side.
o_ops = invert(i_ops)
syms = o_ops.input_symbols()
insert_label = syms.find(self.INSERT)
delete_label = syms.find(self.DELETE)
o_ops.relabel_pairs(ipairs=((insert_label, delete_label),
(delete_label, insert_label)))Args:
alphabet: edit alphabet (an iterable of strings).
insert_cost: the cost for the insertion operation.
delete_cost: the cost for the deletion operation.
substitute_cost: the cost for the substitution operation.
"""
# Left factor; note that we divide the edit costs by two because they also
# will be incurred when traversing the right factor.
match = union(*alphabet).optimize(True)
i_insert = transducer("", "[{}]".format(self.INSERT),
weight=insert_cost / 2).optimize(True)
i_delete = transducer(match, "[{}]".format(self.DELETE),
weight=delete_cost / 2).optimize(True)
i_substitute = transducer(match, "[{}]".format(self.SUBSTITUTE),
weight=substitute_cost / 2).optimize(True)
i_ops = union(match, i_insert, i_delete, i_substitute).optimize(True)
# Right factor; this is constructed by inverting the left factor (i.e.,
# swapping the input and output labels), then swapping the insert and delete
# labels on what is now the input side.
o_ops = invert(i_ops)
syms = o_ops.input_symbols()
insert_label = syms.find(self.INSERT)
delete_label = syms.find(self.DELETE)
o_ops.relabel_pairs(ipairs=((insert_label, delete_label),
(delete_label, insert_label)))
# Computes the closure for both sets of ops.
self._e_i = i_ops.closure().optimize(True)
self._e_o = o_ops.closure().optimize(True)
