用代码帮你了解Python基础(3)

# 1.for...in循环，依次把list或tuple中的每个元素迭代出来
studentNames = ["Willard","ChenJD","ChenBao","LinWenYu"]
for studentName in studentNames:
    print(studentName)
print("------------------------------------------------")
# 计算1-10的累加和
sumOfNums = 0
for num in [1,2,3,4,5,6,7,8,9,10]:
    sumOfNums = sumOfNums + num
print("1-10的累加和是：",sumOfNums)
print("------------------------------------------------")
# 使用range()函数进行整数序列生成，range()函数为左闭右开
# 计算1-1000的累加和
sumOfNums = 0
for num in range(1001):
    sumOfNums += num
print("1-1000的累加和是：",sumOfNums)

# 2.while循环，只要条件满足，就不断循环，条件不满足时退出循环
# 计算100以内的奇数和
sumOfNums = 0
n = 99
while n > 0:
    sumOfNums += n
    n = n -2
print("100以内的奇数累加和为：",sumOfNums)

# 3.使用break语句提前退出循环
n = 1
while n < 20:
    if n > 10:
        break
    print("n的值为：",n)
    n += 1
print("The End.")

# 4.continue语句，跳过当前循环，直接开始下一次循环
n = 10
while n < 20:
    n += 1
    if n == 15:
        continue
    print("n的值为：",n)
print("The End.")

# 5.登录实例
totalFrequency = 3
inputFrequency = 0
userName = input("请输入您的账号：")
passWord = input("请输入您的密码：")
while inputFrequency < totalFrequency:
    if ((userName == "Willard") and (password == "JD584520")):
        print("账号密码正确，登录成功！")
        break
    else:
        print("账号或密码输入错误，登录失败！")
        if (totalFrequency - inputFrequency - 1) == 0:
            break
        print("请重新登录！您还有%d次输入账号密码的机会！"%(totalFrequency - inputFrequency - 1))
        print("----------------------------------------")
    inputFrequency += 1
    userName = input("请重新输入您的账号：")
    password = input("请重新输入您的密码：")

# dict：字典，使用键-值对(key-value)存储；
# 实例：
studentScore = {"Willard":{"Math":100,"Chinese":98,"Eng":90},
               "ChenJD":{"Math":99,"Chinese":100,"Eng":98},
               "ChenBao":{"Math":100,"Chinese":99,"Eng":96}}
print("Willard的成绩是：",studentScore["Willard"])
print("ChenJD的成绩是：",studentScore["ChenJD"])
print("ChenBao的成绩是：",studentScore["ChenBao"])
print("---------------------------------------------")
# 修改元素的值
print("Willard原来的成绩是：",studentScore["Willard"])
studentScore["Willard"] = {"Math":100,"Chinese":100,"Eng":100}
print("修改后Willard的成绩是：",studentScore["Willard"])
print("---------------------------------------------")
# 判断key是否存在
# 1.通过in判断key是否存在
print("判断是否存在'ChenXiaoBao'这个key.\n")
if "ChenXiaoBao" in studentScore:
    print("存在'ChenXiaoBao'这个key.")
else:
    print("不存在'ChenXiaoBao'这个key.")
print("---------------------------------------------")
# 2.通过get()方法，如果key不存在，返回None，或指定的value
print(studentScore.get("Willard"))
print(studentScore.get("Willard"),-1)
print("---------------------------------------------")
# 删除一个key，使用pop(key)
print("删除前的字典：\n",studentScore,"\n")
studentScore.pop("ChenBao")
print("删除后的字典：",studentScore)
# Tips：
# 字典的key必须是不可变对象，如：字符串、整数等，list是可变的；

# 集合：set；是一组key的集合，但不存储value，且key不能重复，具有唯一性；
# 1.创建一个set，提供一个list作为输入集合
setEg = set([1,2,3])
print("集合setEg的内容：",setEg)
print("------------------------------")
# 2.集合的元素唯一性
setEg2 = set([1,1,1,2,3,4,5,3,2])
print("集合setEg2的内容：",setEg2)
print("------------------------------")
# 3.添加元素
setEg = set([1,2,3])
print("添加元素前集合的内容：",setEg)
setEg.add(5)
print("添加元素后集合的内容：",setEg)
print("------------------------------")
# 4.删除元素
setEg = set([1,2,3])
print("删除元素前集合的内容：",setEg)
setEg.remove(1)
print("删除元素后集合的内容：",setEg)
print("------------------------------")
# 5.交集、并集
setOne = set([1,2,3,4,5])
setTwo = set([1,2,4,6])
print("setOne集合的内容：",setOne)
print("setTwo集合的内容：",setTwo)
print("setOne和setTwo的交集：",(setOne & setTwo))
print("setOne和setTwo的并集：",(setOne | setTwo))