用代碼幫你瞭解Python基礎(3)

# 1.for...in循環，依次把list或tuple中的每個元素迭代出來
studentNames = ["Willard","ChenJD","ChenBao","LinWenYu"]
for studentName in studentNames:
    print(studentName)
print("------------------------------------------------")
# 計算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()函數進行整數序列生成，range()函數為左閉右開
# 計算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循環，隻要條件滿足，就不斷循環，條件不滿足時退出循環
# 計算100以內的奇數和
sumOfNums = 0
n = 99
while n > 0:
    sumOfNums += n
    n = n -2
print("100以內的奇數累加和為：",sumOfNums)

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

# 4.continue語句，跳過當前循環，直接開始下一次循環
n = 10
while n < 20:
    n += 1
    if n == 15:
        continue
    print("n的值為：",n)
print("The End.")

# 5.登錄實例
totalFrequency = 3
inputFrequency = 0
userName = input("請輸入您的賬號：")
password = input("請輸入您的密碼：")
while inputFrequency < totalFrequency:
    if ((userName == "Willard") and (password == "JD584520")):
        print("賬號密碼正確，登錄成功！")
        break
    else:
        print("賬號或密碼輸入錯誤，登錄失敗！")
        if (totalFrequency - inputFrequency - 1) == 0:
            break
        print("請重新登錄！您還有%d次輸入賬號密碼的機會！"%(totalFrequency - inputFrequency - 1))
        print("----------------------------------------")
    inputFrequency += 1
    userName = input("請重新輸入您的賬號：")
    password = input("請重新輸入您的密碼：")

# dict：字典，使用鍵-值對(key-value)存儲；
# 實例：
studentScore = {"Willard":{"Math":100,"Chinese":98,"Eng":90},
               "ChenJD":{"Math":99,"Chinese":100,"Eng":98},
               "ChenBao":{"Math":100,"Chinese":99,"Eng":96}}
print("Willard的成績是：",studentScore["Willard"])
print("ChenJD的成績是：",studentScore["ChenJD"])
print("ChenBao的成績是：",studentScore["ChenBao"])
print("---------------------------------------------")
# 修改元素的值
print("Willard原來的成績是：",studentScore["Willard"])
studentScore["Willard"] = {"Math":100,"Chinese":100,"Eng":100}
print("修改後Willard的成績是：",studentScore["Willard"])
print("---------------------------------------------")
# 判斷key是否存在
# 1.通過in判斷key是否存在
print("判斷是否存在'ChenXiaoBao'這個key.\n")
if "ChenXiaoBao" in studentScore:
    print("存在'ChenXiaoBao'這個key.")
else:
    print("不存在'ChenXiaoBao'這個key.")
print("---------------------------------------------")
# 2.通過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("---------------------------------------------")
# 刪除一個key，使用pop(key)
print("刪除前的字典：\n",studentScore,"\n")
studentScore.pop("ChenBao")
print("刪除後的字典：",studentScore)
# Tips：
# 字典的key必須是不可變對象，如：字符串、整數等，list是可變的；

# 集合：set；是一組key的集合，但不存儲value，且key不能重復，具有唯一性；
# 1.創建一個set，提供一個list作為輸入集合
setEg = set([1,2,3])
print("集合setEg的內容：",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的內容：",setEg2)
print("------------------------------")
# 3.添加元素
setEg = set([1,2,3])
print("添加元素前集合的內容：",setEg)
setEg.add(5)
print("添加元素後集合的內容：",setEg)
print("------------------------------")
# 4.刪除元素
setEg = set([1,2,3])
print("刪除元素前集合的內容：",setEg)
setEg.remove(1)
print("刪除元素後集合的內容：",setEg)
print("------------------------------")
# 5.交集、並集
setOne = set([1,2,3,4,5])
setTwo = set([1,2,4,6])
print("setOne集合的內容：",setOne)
print("setTwo集合的內容：",setTwo)
print("setOne和setTwo的交集：",(setOne & setTwo))
print("setOne和setTwo的並集：",(setOne | setTwo))