Python基础第一天

一、内容

二、练习

练习1

题目：使用while循环输出1 2 3 4 5 6 8 9 10

方法一：

图示：

代码：

count = 1
while count < 11:if count != 7:print(count)count += 1

输出结果：

View Code

方法二：

图示：

代码：

count = 0
while count < 10:count += 1if count == 7:continueprint(count)

输出结果：

View Code

练习2

题目：求1-100的所有数的和

图示：

代码：

sum = 0
count = 1
while count < 101:sum = sum + countcount += 1
print(sum)

输出结果：

练习3

题目：输出 1-100 内的所有奇数

图示：

代码：

count = 1
while count < 101:if count % 2 != 0:print(count)count += 1

输出结果：

View Code

练习4

题目：输出 1-100 内的所有偶数

图示：

代码：

count = 1
while count < 101:if count % 2 == 0:print(count)count += 1

输出结果：

View Code

练习5

题目：求1-2+3-4+5 ... 99的所有数的和

图示：

代码：

count = 1
sum1 = 0
sum2 = 0
while count < 100:if count % 2 != 0:sum1 = sum1 + countelse:sum2 = sum2 - countcount += 1
print(sum1 + sum2)

输出结果：

练习6

题目：用户登陆（三次机会重试）

步骤一：实现三次登陆的基本功能

图示：

代码：

user = 'knight'
pwd = 'dk123'
count = 1
while True:if count == 4:print('Too many times!')breakusername = input('Please enter your username:')password = input('Please enter your password:')if username == user and password == pwd:print('Login successfully!')breakelse:print('The username or password you entered is incorrect,Please try again!')count += 1

步骤二：去除BUG并添加功能

1、去除用户输入用户名时左右两边的空格

2、判断用户名是否有值，如果没有则反复让用户输入，并提示请输入用户名

3、判断密码是否有值，如果没有则反复让用户输入，提示请输入密码

4、用户每输错一次便告之用户还有多少次机会

图示：

代码：

user = 'knight'
pwd = 'dk123'
count = 1
while True:if count == 4:print('Too many times!')breakusername = input('Please enter your username:').strip()password = input('Please enter your password:')if not username:print('The username you entered is blank, please re-enter')continueelif not password:print('The password you entered is blank, please re-enter')continueif username == user and password == pwd:print('Login successfully!')breakelse:print('The username or password you entered is incorrect,Please try again!')print('You still have %s chances'%(3-count))count += 1

步骤三：三次登陆锁定

扩展：当同一个用户名的输错次数超过三次时，锁定该用户名

图示：

代码：

user = 'knight'
pwd = 'dk123'
count = 1
times = []  # 用于统计密码输错时的用户名的个数with open('blacklist.txt', 'r', encoding='utf-8') as f_black:black_line = f_black.readlines()   # 将黑名单内容以列表的形式读出来# print(black_line)while True:# 当登陆次数超过3次时提示登陆次数过多，退出程序if count == 4:print('Too many times!')breakusername = input('Please enter your username:').strip()password = input('Please enter your password:').strip()# 判断用户名是否为空if not username:print('The username you entered is blank, please re-enter')continue# 判断密码是否为空elif not password:print('The password you entered is blank, please re-enter')continue# 判断用户名再加上"\n"是否在黑名单的列表里，如果在则提示用户已锁定再退出程序if username + '\n' in black_line:print('Sorry, your account has been locked!')break# 判断用户名和密码是否匹配if username == user and password == pwd:print('Login successfully!')breakelse:print('The username or password you entered is incorrect,Please try again!')print('You still have %s chances' % (3 - count)) # 如果不匹配则提示用户名或密码错误并告之用户还有几次机会times.append(username)  # 将错误的用户名加入至事先定义的times列表中，if times.count(username) == 3:  # 然后计算加入的用户名的个数是否等于三个，如果是则写入至黑名单文件中。with open('blacklist.txt', 'a', encoding='utf-8')as f:f.write(username+'\n')count += 1

练习7

题目：猜年龄

步骤一：实现基本逻辑

图示：

代码：

age = 28
while True:user = int(input('Please enter a number:')) # 强转为整型if user > age:print('Try smaller!')elif user < age:print('Try bigger!')else:print('You got it!')break

步骤二：去除BUG并添加功能

1、去除BUG，当用户输入其它字符时让其重新输入

2、添加猜错时给予三次机会功能

图示：

代码：

age = 28
count = 0
while True:if count == 3:print('You guess too many times')breakuser = input('Please enter a number:').strip()if not user.isdigit():print('Please try again,and you must enter a number!')continueelse:user = int(user)if user > age:print('Try smaller!')elif user < age:print('Try bigger!')else:print('You got it!')breakcount += 1