pythonsymbolsopenfstfst

How to get input symbols from a fst model using the OpenFST python extension?

OpenFST provides a python extension. Is ist possible to read input symbols (isyms) from a compiled FST model using that API?

I can't find the right property or method to do that:

>>> import fst
>>> f = fst.Fst('/home/jan/Downloads/en_us_nostress/model.fst')
>>> dir(f)
['__class__', '__delattr__', '__doc__', '__format__',
'__getattribute__', '__hash__', '__init__', '__new__', '__reduce__',
'__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__',
'__subclasshook__', '_arc_type', '_check_mutating_imethod',
'_fst_type', '_weight_type', 'arcsort', 'closure', 'concat',
'connect', 'decode', 'encode', 'invert', 'minimize', 'project',
'properties', 'prune', 'push', 'relabel', 'reweight', 'rmepsilon',
'topsort', 'union', 'verify', 'write']
>>> dir(fst)
['ACCEPTOR','ACCESSIBLE', 'ACYCLIC', 'ADD_ARC_PROPERTIES',
'ADD_STATE_PROPERTIES', 'ADD_SUPERFINAL_PROPERTIES', 
'ARC_SORT_PROPERTIES', 'BINARY_PROPERTIES', 'COACCESSIBLE',
'COPY_PROPERTIES', 'CYCLIC', 'DELETE_ARC_PROPERTIES', 
'DELETE_STATE_PROPERTIES', 'EPSILONS', 'ERROR', 'EXPANDED', 
'EXTRINSIC_PROPERTIES', 'FST_PROPERTIES', 'Fst',
'FstError', 'FstWarning', 'INITIAL_ACYCLIC', 'INITIAL_CYCLIC',
'INTRINSIC_PROPERTIES', 'I_DETERMINISTIC', 'I_EPSILONS',
'I_LABEL_INVARIANT_PROPERTIES', 'I_LABEL_SORTED', 'MUTABLE',
'NEG_TRINARY_PROPERTIES', 'NON_I_DETERMINISTIC',
'NON_O_DETERMINISTIC', 'NOT_ACCEPTOR', 'NOT_ACCESSIBLE',
'NOT_COACCESSIBLE', 'NOT_I_LABEL_SORTED', 'NOT_O_LABEL_SORTED',
'NOT_STRING', 'NOT_TOP_SORTED', 'NO_EPSILONS', 'NO_I_EPSILONS',
'NO_O_EPSILSONS', 'NULL_PROPERTIES', 'O_DETERMINISTIC', 'O_EPSILONS',
'O_LABEL_INVARIANT_PROPERTIES', 'O_LABEL_SORTED',
'POS_TRINARY_PROPERTIES', 'RM_SUPERFINAL_PROPERTIES',
'SET_ARC_PROPERTIES', 'SET_FINAL_PROPERTIES', 'SET_START_PROPERTIES',
'STATE_SORT_PROPERTIES', 'STRING', 'TOP_SORTED',
'TRINARY_PROPERTIES', 'UNWEIGHTED', 'WEIGHTED',
'WEIGHT_INVARIANT_PROPERTIES', 'Weight', '_Fst', '_MutableFst',
'__builtins__', '__doc__', '__file__', '__name__', '__package__',
'__pyx_capi__', '__test__', '_fst_error_fatal_old',
'_get_compose_filter', '_get_queue_type', '_get_rand_arc_selection',
'_get_replace_label_type', 'arcmap', 'compose', 'convert',
'determinize', 'difference', 'disambiguate', 'epsnormalize',
'equal', 'equivalent', 'intersect', 'isomorphic', 'prune', 'push', 'randequivalent', 'randgen', 'replace', 'reverse', 'rmepsilon',
'shortestdistance', 'shortestpath', 'synchronize']
Solution

  • I suspect that you're using version 1.5.0 of OpenFST in which that feature was unavailable. I believe this was added in version 1.5.1 or so. http://www.openfst.org/twiki/bin/view/News/FstNews

    I'm using 1.5.3 and am able to access the symbol tables with input_symbols and output_symbols.

    >>> dir(fst._Fst)
    ['__class__', '__delattr__', '__doc__', '__format__',
    '__getattribute__', '__hash__', '__init__', '__new__',
    '__pyx_vtable__', '__reduce__', '__reduce_ex__', '__repr__',
    '__setattr__', '__sizeof__', '__str__', '__subclasshook__',
    '_repr_svg_', 'arc_type', 'arcs', 'copy', 'draw', 'final',
    'fst_type', 'input_symbols', 'num_arcs', 'num_input_epsilons',
    'num_output_epsilons', 'output_symbols', 'properties', 'start',
    'states', 'text', 'verify', 'weight_type', 'write']

    There's a little more information available here http://www.openfst.org/twiki/bin/view/FST/PythonExtension under "FST object attributes and properties"