赋值之前引用的局部变量“ a”

Question

i have an assignment that is asking me to create a module with 2 functions. The user is to enter the 3 sides of a triangle, and the two functions will check (a) if the input is valid and (b) what the area of the triangle is.

 def isValid(s1,s2,s3):

    if (s1 + s2<=s3):
         print("Input is invalid.")
    else:
         area(s1,s2,s3)


 def area(s1,s2,s3):
     p = (s1+s2+s3)/2
     a = (p*(p-a)*(p-b)*(p-c))**(.5)
     print("The area of the triangle is: ",a)


s1 = eval(input("input s1: "))
s2 = eval(input("input s2: "))
s3 = eval(input("input s3: "))

isValid(s1,s2,s3)

im getting an error of: UnboundLocalError: local variable 'a' referenced before assignment

not sure where to go from here, getting a little confused. Any help would be appreciated.

Answer 1

You are using the variables a , b and c without having defined them, when calculating the area (stored in the variable a again):

a = (p*(p-a)*(p-b)*(p-c))**(.5)

Perhaps you wanted to use s1 , s2 and s3 here instead:

a = (p * (p - s1) * (p - s2) * (p - s3)) ** .5

Answer 2

change function

 def area(s1,s2,s3):
     p = (s1+s2+s3)/2
     a = (p*(p-a)*(p-b)*(p-c))**(.5)
     print("The area of the triangle is: ",a)

to

def area(s1,s2,s3):
    p = (s1+s2+s3)/2
    a = (p*(p-s1)*(p-s2)*(p-s3))**(.5)
    print("The area of the triangle is: ",a)