2d Array Python :list index out of range

Question

I am new to Python programming and I am trying to write code to check if a DFA( Deterministic Finite Automata) has empty language or not.

I am using 2-d array to store state of the DFA. On executing the code I keep getting list index out of range. How can I fix this?

Below is the code

top=-1
count=0
n=int(input("\nEnter the no of states"))
mat=[[]]
b=[]
print("\nEnter the transition table")
for i in range(0,n):
   for j in range(0,n):
    mat.append(input())
finalState=input("\nEnter the final state:")
startState=input("\nEnter the start state:")      

for i in range(0,n):
   for j in range(0,n):
      if mat[i][j]:
        b[++top]=j
for k in range(top):
      if b[k]==finalState:
      count+=1
if count>0:
print("\nLanguage is  not empty")
else:
print("\nLanguage is empty")

In b[++top]=j I am getting list assignment index out of range — shubhamj
– shubhamj, Commented Sep 23, 2015 at 13:50

Kevin · Accepted Answer · 2015-09-23 14:03:32Z

6

when you make a 2x2 table, you want mat to be [[1,2],[3,4]], but you're getting [[],1,2,3,4] right now.

Instead, try:

mat = []
for i in range(n):
    row = []
    for j in range(n):
        row.append(input())
    mat.append(row)

Also, Python does not have a "++" operator, so b[++top]=j is the same as b[top] = j. If you want to increment top, you have to do that on its own line before you use it to index the list.

On top of that, b has zero elements, so indexing it in any way will cause a crash. If you're trying to increase the size of b by adding new items to it, use append. Then you don't need a top variable at all.

b.append(j)

edited Sep 23, 2015 at 14:03

answered Sep 23, 2015 at 13:45

Kevin

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1 Comment

shubhamj Over a year ago

Really sorry for late reply, and thanks for helping me

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