如何从def语句上方获取变量并将其在def语句中使用？
total_cost = 0
def main():
A = input ( " Big Mac Bacon = a1 \n The BBQ and Bacon Chicken - wrap = a2 \n The Fiery Buffalo Chicken One - wrap = a3 \n Chicken Legend with Cool Mayo = a4 \n Choose a main meal: ")
a1 = float (3.09) # Cost of The Big Mac Bacon
a2 = float (4.59) # Cost of The BBQ and Bacon Chicken
a3 = float (4.59) # Cost of The Fiery Buffalo Chicken One - wrap
a4 = float (4.99) # Cost of Chicken Legend with Cool Mayo
if A == "a1": # If this option is selected, ths price will be added
total_cost = total_cost + a1# This option is selected, ths price will be added
side()
elif A == "a2": # If this option is selected, ths price will be added
total_cost = total_cost + a2# This option is selected, ths price will be added
side()
elif A == "a3": # If this option is selected, ths price will be added
total_cost = total_cost + a3# This option is selected, ths price will be added
side()
elif A == "b4":# If this option is selected, ths price will be added
total_cost = total_cost + a4 # This option is selected, ths price will be added
side()
else:
while A != "a1" or "a2" or "a3" or "a4":
print ( "Please enter a valid answer" )
A = input ( " Big Mac Bacon = a1 \n The BBQ and Bacon Chicken - wrap = a2 \n The Fiery Buffalo Chicken One - wrap = a3 \n Chicken Legend with Cool Mayo = a4 \n Choose a main meal: ")
main()
return total_cost