Question

This program will require you to create a basic parser for an input string that is somewhat like Python. Python has an older parser module and a newer ast module to manage pure Python syntax, but they won't be useful here.

The program will read a data string, identify the control characters, and print out the overall structure of the string. Here's an example

Input String: [{1}]

Output: Number inside a dictionary inside a list

Here are some basic rules for the program:

• The control characters you need to be concerned with are: , { } (dictionary), () (tuple), and ' " (string). Note that all string start with a single quote and end with a double quote (to reduce complexity in your solution).
• The program must print out the structures starting with the innermost first and ending with the outermost
• Once you start getting structure close characters (e.g. ] } " ) you can ignore any new start character structures (e.g. [ } ' )
• You must also identify an errors in the closing order for the structures. Once you identify an error, print an Error message and stop processing

Input String: {[(abc)}]

Output: Characters inside a tuple inside a ERROR

• The input string may have spaces and other erroneous control characters. These can all be ignored and should not print an error message (i.e. only closing characters above that are out of place will cause an error message to be printed).
• The innermost characters will either be reported as a "number" or as "characters" based on their value. Numbers will have only 0-9 and a-z and A-Z in the inner set makes the value "characters."
• In addition to having erroneous characters in the input string, there will also be random digits and characters in the input string. These are not reported and can be ignored. Only the innermost nested characters matter for this exercise.

Answer 1

Python Code:

inpstr = input('Enter the string: ') #get the string from the user
charList = [] #to store the brackets
shouldappend = True #flag to check closing brackets
ischar = False
i=-1
for char in inpstr: #iterating throught each characters
i+=1
if (ord(char) >= 65 and ord(char) <= 90) or (ord(char) >= 97 and ord(char) <= 122): #check if it is a letter
ischar = True
elif (ord(char) >= 48 and ord(char) <= 57): #check if it is a number
pass
if (i+1 < len(inpstr)) and shouldappend == True: #checking for last character
if ((ord(char) >= 48 and ord(char) <= 57) or (ord(char) >= 65 and ord(char) <= 90) or (ord(char) >= 97 and ord(char) <= 122)) and ((ord(inpstr[i+1]) < 65 or ord(inpstr[i+1]) > 90) and (ord(inpstr[i+1]) < 97 or ord(inpstr[i+1]) > 122) and (ord(inpstr[i+1]) < 48 or ord(inpstr[i+1]) > 57)): #check if it is a number
shouldappend = False
if ischar == False:
print('Numbers ', end='')
else:
print('Characters ', end='')
if (char == '(' or char == '{' or char == '[' or char == "'") and shouldappend == True: #check if it is opening bracket
charList.append(char)
elif char == ')': #check if it is closing bracket
shouldappend = False
stackchar = charList.pop(len(charList)-1) #getting the last element of the list
if stackchar != '(': #checking if there is proper opening bracket
print ('inside a ERROR ', end='') #if there isnt printing error then exiting
break
else:
print ('inside a tuple ', end='') #print the output
elif char == '}': #similarly we check for "}"
shouldappend = False
stackchar = charList.pop(len(charList)-1)
if stackchar != '{':
print ('inside a ERROR ', end='')
break
else:
print ('inside a dictionary ', end='')
elif char == ']': #similarly we check for "]"
shouldappend = False
stackchar = charList.pop(len(charList)-1)
if stackchar != '[':
print ('inside a ERROR ', end='')
break
else:
print ('inside a list ', end='')
elif char == '"': #similarly we check for "
shouldappend = False
stackchar = charList.pop(len(charList)-1)
if stackchar != "'":
print ('inside a ERROR ', end='')
break
else:
print ('inside a string ', end='')

Sample Output:

Enter the string: {[(avc)]}
Characters inside a tuple inside a list inside a dictionary