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))