python-zx笔记3-函数

一、调用函数

在交互式命令行通过help(abs)查看abs函数的帮助信息

把函数名赋给一个变量

a = abs

二、定义函数

求解方程：ax2 + bx + c = 0

 # -*- coding: utf-8 -*-

 import math

 def quadratic(a, b, c):
     n = b*b - 4*a*c
     if n < 0:
         return ("此方程无解")
     elif n == 0:
         return b/2*a
     else:
         x1 = (-b + math.sqrt(n))/(2*a)
         x2 = (-b - math.sqrt(n))/(2*a)
         return x1,x2

 # 测试:
 print(quadratic(1,2,1))
 print(quadratic(4,2,2))

 # print('quadratic(2, 3, 1) =', quadratic(2, 3, 1))
 # print('quadratic(1, 3, -4) =', quadratic(1, 3, -4))
 # if quadratic(2, 3, 1) != (-0.5, -1.0):
 #     print('测试失败')
 # elif quadratic(1, 3, -4) != (1.0, -4.0):
 #     print('测试失败')
 # else:
 #     print('测试成功')

三、函数的参数