#This is the main function that will decode binary and show you its value
def main ():
    
#This is the Binary number that the user willwant the program to decode
    binaryInput = input("Enter a number, binary only please > ")
    
    #This is the vale of the expponet, it's value depends oin ther amount of one's and zero's in the binary number
    exponentValue = len(binaryInput)
    totalValue = 0
    
    
    #This if statement will only start if nothing is entered
    if exponentValue < 1:
        
        #This is gonna delete the binary number that the user put in
        del binaryInput
        
        #This deletes the exponets value 
        del exponentValue
        
        #this gets rid  of the total value
        del totalValue
        
        #Prints a message that let's the user know that the program knows that they did not put anything in as a decimal value
        print("I know what you did, only pressed enter huh?  Nice try but I need a Biary number.")
        
        #This restarts the program
        main()
        
    #this will tell the program that the ones are equal to 2 and zeros are 0
    for conversion in range(exponentValue):
    
        #this part says that if there is a zero, it equals zero
        if binaryInput[conversion] =="0":
             actualvalue = 0

        
        #if there is a one in the binary number, it equals 2
        elif binaryInput[conversion] == "1":
            actualvalue = 2
        
        # what happens if the user puts in anything other than ones and zeros
        else:
            
            #shows this message
            print("That's not a Binary number silly, its only 0 and 1")
            
            #This is gonna delete the binary number that the user put in
            del binaryInput
            
            #deletes exponent's value
            del exponentValue
            
            #deletes the total value
            del totalValue
            
            #restarts the program
            main()
            
        #this will give me the true value of the binary number saying that it is the actual value muitiplied by the the exponet value -1 exponent
        trueValue = actualvalue ** (exponentValue -1)
            
            
        #This is just in case the binary number put in is 0, it makes the exponet value equal 1, because 0 to the power of 0 equals 1    
        if  actualvalue == 0 and exponentValue == 1:
            trueValue = 0
        
        
        
        
        #this will make the exponet value go down by one so its accurate
        exponentValue -= 1
        
        
        totalValue += trueValue
        
        #this will show the value 
    print("The decimal value of {} is {}".format(binaryInput, totalValue))     
        
        
        
        
main()

Enter a number, binary only please > 11010
The decimal value of 11010 is 26