Python如何判断三段线能否构成三角形

#!/usr/bin/env python3
#coding = utf-8
def is_triangle(a=0, b=0, c=0): #abc 三条边长
 A = [a,b,c]
 A.sort()   #升序排序
 if A[2] < A[1] +A[0]:
 print("{} is triangle".format(A))
 else:
 print("不构成三角")
def triangle(f):
 a = float(input("第一条边是 = "))
 b = float(input("第二条边是 = "))
 c = float(input("第三条边是 = "))
 f(a, b, c)
triangle(is_triangle) # 常规函数的调用

def main():
  a = float(input('a = '))
  b = float(input('b = '))
  c = float(input('c = '))
  if a + b > c and a + c > b and b + c > a:
    print('周长: %f' % (a + b + c))
    p = (a + b + c) / 2
    area = math.sqrt(p * (p - a) * (p - b) * (p - c))
    print('面积: %f' % (area))
  else:
    print('不能构成三角形')


if __name__ == '__main__':
  main()