python - Importing function to new file not working -

my program designed create module named mytriangle reads 3 sides of triangle , computes area if input valid. if input invalid, display "input invalid". program works beautifully. problem trying import module (everything except main function) on different file. have never done before, , can't find anywhere gives clear instructions. here code:

side1, side2, side3 = eval(input("enter 3 sides in double: "))  def isvalid(side1, side2, side3):      return side1 + side2 > side3 , side1 + side3 > side2 , side2 + side3 > side1   def area(side1, side2, side3):      s = (side1 + side2 + side3) / 2;      totalarea = (s * (s - side1) * (s - side2) * (s - side3)) ** 0.5          return totalarea  def main():        condition = isvalid(side1, side2, side3)      totalarea = area(side1, side2, side3)      if condition:         print("the area of triangle " + str(totalarea))     else:         print("input invalid")  main() 

i tried taking "def main()" part , putting file itself. while naming file rest of code "mytriangle.py"

import mytriangle def main():        condition = isvalid(side1, side2, side3)      totalarea = area(side1, side2, side3)      if condition:         print("the area of triangle " + str(totalarea))     else:         print("input invalid")  main() 

when run program, asks "enter 3 sides in double:". when put numbers in (for example: 1, 1, 1), says "name 'isvalid' not defined. not sure if importing on correctly or what. life of me, cannot figure out. little please?

when import mytriangle, defining mytriangle other module. variables defined in module accessed attributes of mytriangle. can use mytriangle.isvalid(...) instead of isvalid(...). alternatively, from mytriangle import * instead of import mytriangle. using from mytriangle import * puts variables defined in mytriangle local namespace can accessed without putting mytriangle @ beginning.