Using Python to guess whether a string in Base64

detect_base64.py

# Found at https://stackoverflow.com/a/45928164/364088
#
# Not flawless
#
import base64                                                                                                                                                   
#                                                                                                                                                                
def isBase64(sb):                                                                                                                                               
    try:                                                                                                                                                        
        if isinstance(sb, str):                                                                                                                                 
            # If there's any unicode here, an exception will be                                                                                                 
            #thrown and the function will return false                                                                                                          
            sb_bytes = bytes(sb, 'ascii')                                                                                                                       
        elif isinstance(sb, bytes):                                                                                                                             
            sb_bytes = sb                                                                                                                                       
        else:                                                                                                                                                   
            raise ValueError("Argument must be string or bytes")                                                                                                
        #                                                                                                                                                       
        return base64.b64encode(base64.b64decode(sb_bytes)) == sb_bytes                                                                                         
    except Exception:                                                                                                                                           
        return False                                                                                                                                            
                                                                                                                                                                
def main():                                                                                                                                                     
    print(isBase64('hello'))                                                                                                                                    
                                                                                                                                                                
                                                                                                                                                                
if __name__ == "__main__":                                                                                                                                      
    main()                                                                                                                                                      
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