fst_creation_example

compile_fst.sh

#!/usr/bin/env bash

python create_fst.py | fstcompile --isymbols=chars.syms --osymbols=chars.syms - rosebud.bin.fst

create_char_symbol_table.py

EPS = "<epsilon>"

chars = "abcdefghijklmnopqrstuvwxyz"

def format_symbol_table_line(symbol, index):
  """Format a line of the chars.syms file 
  http://www.openfst.org/twiki/bin/view/FST/FstQuickTour#CreatingShellFsts
  """
  pass

print(format_symbol_table_line(EPS, 0))

for i, c in enumerate(chars, 1):
    print(format_symbol_table_line(c, i))

create_fst.py

EPS = "<epsilon>"


def format_arc(src, dst, ilabel, olabel, weight=0):
    """Create an Arc, aka a line of an openfst text format file
    http://www.openfst.org/twiki/bin/view/FST/FstQuickTour#CreatingShellFsts
    """
    pass


# Let's create a simple acceptor for the word rosebud
letters = list('rosebud')

# Start input from state 1. State 0 will be the accept state
s = 1
for i in range(0, len(letters)):
    # Not finished yet. Create an arc for letter at position i and proceed to next state
    print(
        format_arc(
            s, s + 1, letters[i], letters[i], weight=0
        )
    )
    
    s += 1
    
    if i == len(letters) - 1:
        # Reached end of word. Create epsilon transition to the accept state
        print(
            format_arc(
                s, 0, EPS, EPS, w=0
            )
        )

# Print acceptor state
print(0)