How to implement nfa in python

#nfa simulation for (a|b)*abb
#state 4 is a trap state


import sys

def main():
    transition = [[[0,1],[0]], [[4],[2]], [[4],[3]], [[4],[4]]]
    input = raw_input("enter the string: ")
    input = list(input) #copy the input in list because python strings are immutable and thus can't be changed directly
    for index in range(len(input)): #parse the string of a,b in 0,1 for simplicity
        if input[index]=='a':
            input[index]='0' 
        else:
            input[index]='1'

    final = "3" #set of final states = {3}
    start = 0
    i=0  #counter to remember the number of symbols read

    trans(transition, input, final, start, i)
    print "rejected"



def trans(transition, input, final, state, i):
    for j in range (len(input)):
        for each in transition[state][int(input[j])]: #check for each possibility
            if each < 4:                              #move further only if you are at non-hypothetical state
                state = each
                if j == len(input)-1 and (str(state) in final): #last symbol is read and current state lies in the set of final states
                    print "accepted"
                    sys.exit()
                trans(transition, input[i+1:], final, state, i) #input string for next transition is input[i+1:]
        i = i+1 #increment the counter


main()

Source: stackoverflow.com

Similar codes

1 vote266 views1 answer
Flask redirect to url
Python
0 vote256 views1 answer
Python django os error
Python
0 vote254 views1 answer
Convert excel cellname to index python
Python
2 votes313 views1 answer
Skcikit learn decision tree
Python
2 votes245 views1 answer
Python copy a 2D list
Python
0 vote269 views1 answer
Format numbers in column to percentage in python
Python
0 vote245 views1 answer
Mad python
Python
9 votes294 views1 answer
How do you change a string to only uppercase in python
Python
28 votes320 views2 answers
Simple python for loop print 1 to 5
Python
1 vote263 views2 answers
Python 7zip extract
Python