Convert Infix To Prefix Notation.py

"""nput: A * B + C / D
Output: + * A B/ C D 

Input: (A – B/C) * (A/K-L)
Output: *-A/BC-/AKL"""

def isOperator(c):
    return (not c.isalpha()) and (not c.isdigit())
 
 
 
# Function to get the priority of operators
def getPriority(c):
    if c == '-' or c == '+':
        return 1
    elif c == '*' or c == '/':
        return 2
    elif c == '^':
        return 3
    return 0
 
 
   
# Function to convert the infix expression to postfix
def infixToPostfix(infix):
    infix = '(' + infix + ')'
    l = len(infix)
    char_stack = []
    output = ""
 
    for i in range(l):
         
        # Check if the character is alphabet or digit
        if infix[i].isalpha() or infix[i].isdigit():
            output += infix[i]
             
        # If the character is '(' push it in the stack
        elif infix[i] == '(':
            char_stack.append(infix[i])
         
        # If the character is ')' pop from the stack
        elif infix[i] == ')':
            while char_stack[-1] != '(':
                output += char_stack.pop()
            char_stack.pop()
         
        # Found an operator
        else:
            if isOperator(char_stack[-1]):
                if infix[i] == '^':
                    while getPriority(infix[i]) <= getPriority(char_stack[-1]):
                        output += char_stack.pop()
                else:
                    while getPriority(infix[i]) < getPriority(char_stack[-1]):
                        output += char_stack.pop()
                char_stack.append(infix[i])
 
    while len(char_stack) != 0:
        output += char_stack.pop()
    return output
 
 
 
# Function to convert infix expression to prefix
def infixToPrefix(infix):
    l = len(infix)
 
    infix = infix[::-1]
 
    for i in range(l):
        if infix[i] == '(':
            infix[i] = ')'
        elif infix[i] == ')':
            infix[i] = '('
 
    prefix = infixToPostfix(infix)
    prefix = prefix[::-1]
 
    return prefix
 
 
 
# Driver code
if __name__ == '__main__':
    s = "x+y*z/w+u"
     
    # Function call
    print(infixToPrefix(s))
    
    
  #code from geeksforgeeks