1.关于控制结构

控制结构主要包括：顺序结构、选择结构、循环结构。描述如下：

通过5个简单实例，熟悉下python控制结构。

2.实例

实例1:求圆的半径和面积

#from...import语句允许我们直接导入所需的项，避免了冗长的模块名前缀，使代码更加简洁。
from math import pi
r=float(input("输入圆的半径："))
#计算圆的周长
perimeter=2*pi*r
#计算圆的面积
area=pi*(r**2)
print(f"圆的周长:{perimeter},圆的面积:{area}")

输出结果:
输入圆的半径：1.5
圆的周长:9.42477796076938,圆的面积:7.0685834705770345

实例2:找出符合条件的人

people={
    "li lei":{"age":20,"sex":"male","area":"shang hai"},
    "song lei":{"age":33,"sex":"male","area":"chong qing"},
    "zhang lei":{"age":21,"sex":"male","area":"hang zhou"},
    "han mei mei":{"age":21,"sex":"female","area":"shang hai"}
}
area_set={"shang hai","chong qing"}

names=[]

for key,value in people.items():

    area=value['area']
    sex=value['sex']
    age=value['age']
    # 在area_set集合中，男性，年纪[10,20]或者[30，40]
    if (area in area_set ) and (sex=='male') and ((age>=10 and age<=20) or (age>=30 and age<=40)):
        names.append(key)

print(names)

输出结果：
['li lei', 'song lei']

实例3:找出不同年龄段的人

people={
    "li lei":{"age":20,"sex":"male","area":"shang hai"},
    "song lei":{"age":33,"sex":"male","area":"chong qing"},
    "zhang lei":{"age":21,"sex":"male","area":"hang zhou"},
    "han mei mei":{"age":21,"sex":"female","area":"shang hai"}
}
area_set={"shang hai","chong qing"}

names={"1-10":[],"11-20":[],"21-30":[],"31-40":[],"41-100":[]}

for key,value in people.items():

    age=value['age']
   
    if age<=10 :
        names['1-10'].append(key)
    elif age<=20 :
        names['11-20'].append(key)
    elif age<=30 :
        names['21-30'].append(key)
    elif age<=40 :
        names['31-40'].append(key)
    else:
        names['41-100'].append(key)

print(names)

输出结果：
{'1-10': [], '11-20': ['li lei'], '21-30': ['zhang lei', 'han mei mei'], '31-40': ['song lei'], '41-100': []}

实例4:直到输入'quit'退出

message=input("请输入:")
while message!='quit':
    print(message)
    message = input("请输入:")
print('结束')

#相同功能实现,break跳出循环
message=input("请输入:")
while True:
    if message=='quit':
        break
    print(message)
    message = input("请输入:")
print('结束')

输出结果：
请输入:123
123
请输入:456
456
请输入:quit
结束

实例5:打印1-10的奇数

number=0
while number<10:
    number += 1
    if number %2 ==0:
        continue
    print(number)

输出结果：
1
3
5
7
9