Please Help me in understanding this code line by line

import token import ply.lex as lex tokens=( 'NUMBER', 'FLOAT', 'IDENTIFIER', 'LPAREN', 'RPAREN', 'PLUS', 'MINUS', 'DIVIDE', 'EQUAL', 'TIMES', 'KEYWORD', 'COLON' )

t_NUMBER=r'[0-9]+' t_FLOAT=r'[0-9][.][0-9]*' t_IDENTIFIER= r' [a-zA-Z_][a-zA-Z0-9]*' t_LPAREN =r'\(' t_RPAREN =r'\)' t_PLUS = r'\+' t_MINUS = r'\-' t_DIVIDE = r'/' t_EQUAL = r'=' t_TIMES = r'\*' t_COLON = r';'

def t_KEYWORD(t): r'int|real|char|float|string|double' return t

def t_error(t): print("Illegal character '%s'" % t.value[0]) t.lexer.skip(1)

lexer = lex.lex() data='25*3+2' element=[] lexer.input(data) while True: Tok = lexer.token() if not Tok: break element.append(Tok.value) input="" for values in element: if values.isdigit(): input+='digit' else: input+=values print(input)

Flag = 1 Stack = ['0'] Rules = ['+','*','(', ')', 'digit', '$', 'L', 'E' ,'T', 'F'] S_R = ['S5', 'S6', 'S7', 'S8','S12','R1', 'R2', 'R3', 'R4', 'R5', 'R6', 'R7'] Production = ['E','E+T','T', 'T*F', 'F', '(E)', 'digit'] Replace = ['L', 'E', 'E', 'T', 'T', 'F', 'F'] Parser_Table = [ ['Error', 'Error', 'S5', 'Error', 'S6', 'Error', 'Error', '1', '2', '3', '4'], ['Error', 'Error', 'Error', 'Error', 'Error', 'Accept', 'Error', 'Error', 'Error', 'Error', 'Error'], ['S7', 'Error', 'S5', 'Error', 'S6', 'R1', 'Error', 'Error', 'Error', 'Error', 'Error'], ['R3', 'S8', 'Error', 'R3', 'Error', 'R3', 'Error', 'Error', 'Error', 'Error', 'Error'], ['R5', 'R5', 'Error', 'R5', 'Error', 'R5', 'Error', 'Error', 'Error', 'Error', 'Error'], ['Error', 'Error', 'S5', 'Error', 'S6', 'Error', 'Error', 'Error', '9', '3', '4'], ['R7', 'R7', 'Error', 'R7', 'Error', 'R7', 'Error', 'Error', 'Error', 'Error', 'Error'], ['Error', 'Error', 'S5', 'Error', 'S6', 'Error', 'Error', 'Error', 'Error', '10', '4'], ['Error', 'Error', 'S5', 'Error', 'S6', 'Error', 'Error', 'Error', 'Error', 'Error', '11'], ['S7', 'Error', 'Error', 'S12', 'Error', 'Error', 'Error', 'Error', 'Error', 'Error', 'Error'], ['R2', 'S8', 'Error', 'R2', 'Error', 'R2', 'Error', 'Error', 'Error', 'Error', 'Error'], ['R4', 'R4', 'Error', 'R4', 'Error', 'R4', 'Error', 'Error', 'Error', 'Error', 'Error'], ['R6', 'R6', 'Error', 'R6', 'Error', 'R6', 'Error', 'Error', 'Error', 'Error', 'Error'], ] from random import seed from random import randint text = input global p,pop, post, temp, i, a ,row temp=0 print('length of text : ', len(text))

def Reduce(msg, Product, a): global p, pop, post, temp, i , row

if text[a]==Rules[i]: temp=Stack[len(Stack)-1] post=int(temp) print("Start new stack is: ", post) print("new SR is: ", Parser_Table[post][i])

for j in range(0,len(S_R),1): if Parser_Table[post][i]==S_R[j]: print('Condition is match is : ', S_R[j]) msg = S_R[j] if msg[0] =='S': Stack.append(text[a]) Stack.append(msg[1]) print('Product rule second value is: ',msg[1]) print(Stack) if Flag =='1': i=i+1

elif msg[0] =='R': print(Stack) temp=Stack[len(Stack)-1] post= int(temp) p = int(msg[1]) print('Product rule second value is: ',p) pop = len(Product[p-1])*2 print('pop values: ', pop) for k in range(0,pop,1): Stack.pop() Stack.append(Replace[p-1]) ss= Replace[p-1] row = int(Stack[len(Stack)-2]) for i in range(0,len(Rules),1): if ss==Rules[i]: print('new stack is: ', post) print('last value of Stack is: ', Parser_Table[row][i]) Stack.append(Parser_Table[row][i]) print(Stack) if Stack[len(Stack)-2] == 'S': print(Stack) else: Reduce(msg,Product,a) a=0 check = 2 stop =len(text) print('while loop is going to stop on: ',stop) while a< stop: print('-------------------') print('your a is ',a, ' and input is ', text[a])

for i in range(0,len(Rules),1): if text[a] ==Rules[i]: temp =Stack[len(Stack)-1] post = int(temp) print('Start new stack is: ', post) print('new SR is: ',Parser_Table[post][i])

if Parser_Table[post][i]=='Accept': Stack.append(Parser_Table[post][i]) print(Stack) a=a+1 break if Parser_Table[post][i]=='Error': print("invalid grammar not passed") a=a+1 break else: for j in range(0,len(S_R),1): if Parser_Table[post][i] ==S_R[j]: print('Condition is match is : ',S_R[j]) msg = S_R[j]

if msg[0] == 'S': Stack.append(text[a]) Stack.append(msg[1]) print('Product rule second value is: ',msg[1]) print(Stack) if Flag ==1: a=a+1 elif msg[0] == 'R': Flag =0 Reduce(msg,Production,a) else: print("Error_Occurred")

if Stack[len(Stack)-check] =='S': a=a+1 check = check+1 break