Python学习第四天

1. for循环和break语句　

for i in range(3):　　# i的取值 [0,1,2,3)
    print(i)

以下代码输出1 到 101的所有奇数

for i in range(1,101,2):    # 2是步长
    print("loop:",i)

30 到40之间的值不打印

for i in range(1,101,2):    # 2是步长
    if i<30 or i>40:
        print("loop:",i)

简单的登录案例

userName = "Kevin"
password = "123456"

# 有5次输错密码的机会
for i in range(5):
    userName1 = input("Please Enter Your UserName:")
    password1 = input("Please Enter Your Password:")
    if userName == userName1 and password == password1:
        print("Congratulations %s ! Login Success" %userName)
        break;  # 跳出，中断
    else:
        print("UserName Or Password Is Error!")

5次登录失败的时候打印提示语句

userName = "Kevin"
password = "123456"
flag = True
# 有5次输错密码的机会
for i in range(5):
    userName1 = input("Please Enter Your UserName:")
    password1 = input("Please Enter Your Password:")
    if userName == userName1 and password == password1:
        print("Congratulations %s ! Login Success" %userName)
        flag = False
        break;  # 跳出，中断
    else:
        print("UserName Or Password Is Error!")
if flag:
    print("Are you shameless?")

或者 for循环后面跟着else语句

userName = "Kevin"
password = "123456"

# 有5次输错密码的机会
for i in range(5):
    userName1 = input("Please Enter Your UserName:")
    password1 = input("Please Enter Your Password:")
    if userName == userName1 and password == password1:
        print("Congratulations %s ! Login Success" %userName)
        break;  # 跳出，中断
    else:
        print("UserName Or Password Is Error!")
else:
    print("Are you shameless?")

2. continue语句和while语句

　　while 循环实现5次输入密码和用户名

userName = "Kevin"
password = "123456"

# 有5次输错密码的机会
count = 0
while count < 5:
    userName1 = input("Please Enter Your UserName:")
    password1 = input("Please Enter Your Password:")
    if userName == userName1 and password == password1:
        print("Congratulations %s ! Login Success" %userName)
        break;  # 跳出，中断
    else:
        print("UserName Or Password Is Error!")
    count = count + 1
else:
    print("Are you shameless?")

当输入错误出现3次，由用户决定是否继续尝试

userName = "Kevin"
password = "123456"

# 有5次输错密码的机会
count = 0
while count < 5:
    userName1 = input("Please Enter Your UserName:")
    password1 = input("Please Enter Your Password:")
    if userName == userName1 and password == password1:
        print("Congratulations %s ! Login Success" %userName)
        break;  # 跳出，中断
    else:
        print("UserName Or Password Is Error!")
    count = count + 1
    if count == 3:
        keepTry = input("Do your want to try more times ?[y/n]")
        if keepTry == "y":
            count = 0
else:
    print("Are you shameless?")

continue结束本次循环

for i in range(10):
    if i < 5:
        continue    # 结束本次循环，进入下一次循环
    print(i)　　　　　　# 打印的值是5到9

3. Python的数据结构

　　列表数据

a = ["张三","李四","王五","赵信","内瑟斯"]     # 列表a,类似java中的数组

　　列表查询，获取列表的数据

a = ["张三","李四","王五","赵信","内瑟斯"]     # 列表a,类似java中的数组
print(a[3])     # 列表下表从0开始，打印出 赵信
print(a[1:3])   # 打印出 ['李四', '王五']，出来的结果仍然是列表
print(a[1:])    # 打印出 ['李四', '王五', '赵信', '内瑟斯']
print(a[1:-1])  # 打印出 ['李四', '王五', '赵信']
print(a[1:-1:2])# 打印出 ['李四', '赵信']
print(a[3::-2]) # 打印出 ['赵信', '李四']

　　向列表中添加元素，append(self,object),insert(self,index,object)

b = ["张三","李四","王五","赵信","内瑟斯"]
b.insert(5,"泰达米尔")
print(b[5])
b.append("Boy Next Door")   # 默认插入到列表最后一个位置
print(b[0:-1])              # ['张三', '李四', '王五', '赵信', '内瑟斯', '泰达米尔']

　　列表元素的修改

c = ["张三","李四","王五","赵信","内瑟斯"]
c[2] = "亚特兰蒂斯"
print(c)
c[1:3] = ["纽约","华盛顿","莫斯科"]
print(c)
#　　元素的删除
c.remove("纽约")
print(c)            # ['张三', '华盛顿', '莫斯科', '赵信', '内瑟斯']
c.pop(1)
print(c)
del c[0]            
print(c)

4. 列表的内置方法

a = ["2","2","3","44","33","2","3"].count("2")  # 计算列表中元素出现的次数
print(a)

a = ["张三","李四","王五","赵6","朱七"]
b = ["2","2","4"]
a.extend(b)     # 在列表a后面添加列表b
print(a)
print(b)

index = a.index("李四")   # 获取 李四所在列表的索引值
print(index)

b.reverse()     # 列表反转
print(b)

c = [1,2,3,4,45,8,5,9,100,23]
c.sort()        # 从小到大排序
print(c)

秒客网

Python学习第四天

相关文章