How can I fix or improve this code? Invalid syntax on except part

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Python

validation

I need to make a program that uses class function to ask users to input a string of parenthesis and I need to give an error message if they entered a non-parenthesis.

What I have tried:

def valid_char():
    while True:
        char="("")""[""]""{""}""()[]{}"
        
        try:
            int_char=char(input("Enter your string:")
            
        except ValueError:
            print("Error, please input a valid parenthesis:")
            
        elif:
            print("This is your string", int_char)
            break
        
valid_char()

This is the result:

except ValueError:
         ^
SyntaxError: invalid syntax