class PostfixInterpreter:

def $\_\_$init$\_\_($self$)$:

self.stack $=[]$

self.symbol$\_$table $=\{\}$

def evaluate$($self$,$ expression$)$:

tokens $=$ expression.split$()$

for token in tokens:

if token.isnumeric$()$ or $($token$.$startswith$(\text{'}-\text{'})$ and token$[1$:$].$isnumeric$())$:

# Operand: Push onto the stack

self.stack.append$($int$($token$))$

elif token.isalpha$()$ and $($token$.$isupper$()$ or token.islower$())$ and len$($token$)==1$:

# Variable: Push its value onto the stack

if token in self.symbol$\_$table:

self.stack.append$($self$.$symbol$\_$table$[$token$])$

else:

raise ValueError$($f$"$Variable $\{$token$\}$ not defined."$)$

elif token $==\text{'}=\text{'}$:

# Assignment: Pop value from stack and assign to variable

if len$($self$.$stack$)<2$:

raise ValueError$("$Not enough operands for assignment."$)$

value $=$ self.stack.pop$()$ # Corrected order of operations

variable $=$ self.stack.pop$()$

self.symbol$\_$table$[$variable$]=$ value

elif token in $\{\text{'}+\text{'},\text{'}-\text{'},\text{'}*\text{'},\text{'}/\text{'},\text{'}^\text{'}\}$:

# Operator: Pop operands, perform operation, and push result

if len$($self$.$stack$)<2$:

raise ValueError$("$Not enough operands for operator."$)$

operand$2=$ self.stack.pop$()$

operand$1=$ self.stack.pop$()$

result $=$ self.perform$\_$operation$($token$,$ operand$1,$ operand$2)$

self.stack.append$($result$)$

else:

raise ValueError$($f$"$Invalid token: $\{$token$\}")$

if len$($self$.$stack$)==1$:

return self.stack$[0]$

else:

raise ValueError$("$Invalid expression"$)$

def perform$\_$operation$($self$,$ operator, operand$1,$ operand$2)$:

if operator $==\text{'}+\text{'}$:

return operand$1+$ operand$2$

elif operator $==\text{'}-\text{'}$:

return operand$1-$ operand$2$

elif operator $==\text{'}*\text{'}$:

return operand$1*$ operand$2$

elif operator $==\text{'}/\text{'}$:

if operand$2==0$:

raise ValueError$("$Division by zero"$)$

return operand$1/$ operand$2$

elif operator $==\text{'}^\text{'}$:

return operand$1**$ operand$2$

def main$()$:

print$("$Postfix$++$ Interpreter $-$ Enter expressions or type 'exit' to quit"$)$

interpreter $=$ PostfixInterpreter$()$

while True:

try:

expression $=$ input$(">")$

if expression.lower$()==$ 'exit':

break

result $=$ interpreter.evaluate$($expression$)$

print$("$Result:$",$ result$)$

print$("$Symbol Table:", interpreter.symbol$\_$table$)$

except Exception as e:

print$($f$"$Error: $\{$str$($e$)\}")$

finally:

interpreter.stack.clear$()$

if $\_\_$name$\_\_=="\_\_$main$\_\_"$:

main$()$

so the problem in this code is that each time i try to enter a variable for example x $3=$ it would give me an error of Variable x not defined was wondering if someone could solve this for me