2、Python自学第二天（if判断，for循环，while循环）

 1 """================ if判断 begin ======================
 2 
 3 # 输入一个年龄，判断是成年人还是小孩
 4 age = input(‘请输入年龄‘)
 5 if int(age)>=18:
 6     print(‘成年人‘)
 7     exit()
 8 print(‘小孩‘)
 9 
10 # 输入一个数字，判断是奇数还是偶数
11 num = input(‘请输入一个数字‘)
12 if int(num) % 2 == 0:
13     print(‘偶数‘)
14     exit()
15 print(‘奇数‘)
16 
17 # 输入一个月份，判断是哪个季节，python中没有 && , || ，用 and 或 or 来表示
18 season = int(input(‘请输入一个月份：‘))
19 if season >=3 and season <=5:
20     print(‘春季‘)
21 elif season >=6 and season <=8:
22     print(‘夏季‘)
23 elif season >=9 and season <=11:
24     print(‘秋季‘)
25 else:
26     print(‘冬季‘)
27 
28 # 练习
29 小明身高1.75，体重80.5kg。请根据BMI公式（体重除以身高的平方）帮小明计算他的BMI指数，并根据BMI指数：
30 
31 低于18.5：过轻
32 18.5-25：正常
33 25-28：过重
34 28-32：肥胖
35 高于32：严重肥胖
36 bmi = 80.5 / pow(1.75,2)
37 if bmi < 18.5:
38     str = ‘过轻‘
39 elif bmi >= 18.5 and bmi < 25:
40     str = ‘正常‘
41 elif bmi >=25 and bmi < 28:
42     str = ‘过重‘
43 elif bmi >=28 and bmi < 32:
44     str = ‘肥胖‘
45 else:
46     str = ‘严重肥胖‘
47 print(str)
48 
49 =================== if判断 end ========================"""
50 
51 
52 """=============== for 循环 begin ============================
53 
54 name = [‘tom‘,‘bob‘,‘tim‘]
55 for n in name:
56     print(n)
57     
58 # 用for循环计算1-10的和
59 sum = 0
60 nums = [1,2,3,4,5,6,7,8,9,10]
61 for i in nums:
62     sum += i
63 print(sum)
64 
65 # 用for循环计算1-100的值，range(x,y)函数用来生成一个大于x，小于y的列表，如果range(z)一个参数的情况下会生成一个大于等于
66 0，小于101的列表
67 sum = 0
68 for i in range(1,101):
69     sum += i
70 print(sum)
71 
72 ================== for 循环 end============================"""
73 
74 """=============== while 循环 begin =============================
75 
76 # 用while循环计算1-10的和
77 i = 1
78 sum = 0
79 while i<=10:
80     sum += i
81     i+=1
82 print(sum)
83 
84 # 用while循环逆向输出10-1
85 num = 10
86 while num>=0:
87     print(num)
88     num = num-1
89     
90 ================== while 循环 end ====结束时间：2018:11-23 0:06========================"""