Python学习笔记5程序的控制结构

1、分支结构

（1）单分支结构

（2）二分支结构

（3）多分支结构

条件判断

（4）程序的异常处理

2、实例：身体质量指数BMI

思路一（国内，稍作修改就是国际）：

思路二：

 height,weight = eval(input("请输入身高（米）和体重（公斤）[逗号隔开]"))
 bmi = weight / pow(height,2)
 print("BMI 数值为:{:.2f}".format(bmi))
 who, nat = "", ""
 if bmi < 18.5:
     who, nat = "偏瘦","偏瘦"
 elif 18.5 <= bmi < 24:
     who, nat = "正常","正常"
 elif  24 <= bmi < 25:
     who, nat = "正常","偏胖"
 elif  25 <= bmi < 28:
     who, nat = "偏胖","偏胖"
 elif  28 <= bmi < 30:
     who, nat = "偏胖","肥胖"
 else:
     who, nat = "肥胖","偏胖"
 print("BIM指标为：国际'{0}',国内‘{1}’".format(who,nat))
     

3、程序的循环结构

字符串遍历循环

列表遍历循环

文件遍历循环

小结

无限循环

循环控制保留字

循环的高级用法

4、random库的使用

5、实例：圆周率的计算

加斜杠后可以写在两行

 from random import random
 from time import perf_counter
 DARTS = 1000*1000
 hits = 0.0
 start = perf_counter()
 for i in range(1,DARTS+1):
     x,y = random(), random()
     dist = pow(x**2 + y**2,0.5)
     if dist <= 1.0:
         hits = hits + 1
 pi = 4 * (hits/DARTS)
 print("圆周率值是：{}".format(pi))
 print("运行时间是：{:.5f}s".format(perf_counter()-start))