The input and while loops python

The input and while using python

A, Python input () function: obtaining user input string

Python3.x in input () function accepts a standard input data, return type string.

Python2.x in input () is equal to eval(raw_input(prompt)), for acquiring the input console.

the raw_input () will look at all the input as a string, return a string type. The input () having its own characteristics in the treatment of a pure digital input, it returns the type of the input digital (int, float).

Note: input () and the raw_input () function can receive the two strings, but the raw_input () reads the direct input console (any type of input that can be received). As for the input (), it hopes to be able to read a legitimate expression of python, that when you enter the string you must use quotation marks to enclose it up, otherwise it will lead to a SyntaxError.

Unless) there is special need for input (, otherwise we are generally recommended to use raw_input () to interact with the user.

Note: python3 in input () received a default str type.

Function Syntax

input([prompt])

Parameter Description:

• prompt: prompt

Solve the problem:

• input data obtained in the end is what type
• Receiving input of a plurality of input parameters, it is how to unpack
• If the number of uncertain input, how to deal with
• To determine whether the input is not a float
• To the input format of the output parameters, the parameters can be predetermined, or a float or int str

1, an example

# 用户输入
# 提示输入内容
pet = input ('请输入您最喜欢的宠物名称：')
print(pet)

Output:

请输入您最喜欢的宠物名称：猫咪
猫咪

2, lucky number

In python 3 years, things got everything input, are str type (available type () type of view)

good_luck_num = input('请输入你的吉祥号码：')
print(type(good_luck_num))
print('您输入的是：'+good_luck_num)

Output:

请输入你的吉祥号码：9898998
<class 'str'>
您输入的是：9898998

There are input and raw_input in python2 in

• raw_input enjoy are the type str
• automatically generates input type according to the type of input data

We can use Python's built-in function to convert a string into a desired type, such as:

• int (String) String to be converted int type;
• float (String) String to be converted float type;
• bool (String) String to be converted bool type.

3, was selected supermarkets

print('---------超市购物系统---------')
print('1.电子产品 2.化妆品 3.生活用品 4.书籍')
# print('请选择您要购买的产品类型：')
product_type = input('请选择您要购买的产品类型:')
# 判断输入的序号
if product_type == '1':
    print('电子产品')
elif product_type =='2':
    print('化妆品')
elif product_type =='3':
    print('生活用品')
elif product_type =='4':
    print('书籍')
else:
    print('只能输入1~4的数字')

Output:

---------超市购物系统---------
1.电子产品 2.化妆品 3.生活用品 4.书籍
请选择您要购买的产品类型:4
书籍

4, small practice

(1) Write a program that asks the user's favorite job in the IT industry, and outputs a message such as: "My favorite position is the Python automated operation and maintenance."

gz = input('您最喜欢的IT从业岗位：')
print('我最喜欢的岗位是'+gz)

Output:

您最喜欢的IT从业岗位：Python自动化运维
我最喜欢的岗位是Python自动化运维

(2) Write a program that asks students to complete homework today yet? If you enter "y", the output "Today's job done"; if you enter "no", then the output "Today's work will take some time to complete."

zy = input('今天的作业完成了吗？：（y/n）')
if zy ==  'y':
    print('今天的作业完成了')
elif zy == 'n':
    print('今天的作业还需要一段时间才能完成')

Output:

今天的作业完成了吗？：（y/n）y
今天的作业完成了

(3) allows the user to enter a three-digit output this number is not a palindrome.

num = input('输入一个三位数')
num2 = num[::-1]
print(num2)
if num == num2:
    print('这是个回文数')
elif num != num2:
    print('这是个普通数字')

Output:

输入一个三位数121
121
这是个回文数

Two, Python While Loops

Python programming while statement for executing a program loop, i.e., under certain conditions, implementation of certain program loop, the same processing task needs to repeat the process. The basic form:

while 判断条件(condition)：
    执行语句(statements)……

Execute statement may be a single statement or a block. Determination condition can be any expression, in any non-zero value, or a non-empty (null) are true.

When the determination condition false false, the cycle ends.

Performing the following flow chart:

Gif demonstration Python while statement is executed

A bit more complex:

1, examples: (while loop: If this thing is repetitive to do)

num = 1
while num<10:
    print(num,end=" ")
    num = num+1

Output:

1 2 3 4 5 6 7 8 9 

2, while loop, calculates the sum of the even-numbered 1-100.

#创建一个变量x初始化为2
x = 2
#创建一个变量sum初始化为0
sum = 0
#使用while循环求出0-100所有偶数的和
while x <= 100 :
    sum += x 
    x += 2
#打印输出求和结果
print(sum)

Output:

2550

3. Write a program to simulate user login, authentication username and password, maximum input for 3 times, otherwise lock the user.

count = 3
users= 'xgp'
password= '123.com'
i = 3
while i > 0 and i < 4:
    # 输入提示
    user = input('请输入您的用户名：')
    passwd = input('请输入您的密码：')
    # 判断用户名和密码
    if user == users and passwd == password:
        print('登陆成功')
        break
    else:
    # 登陆统计次数
        i = i - 1
        if i == 0:
            print('账号锁定')

相比较上面的简单一点
count = 3
while count>0: 
    name = input('请输入用户名：')
    password = input('请输入密码：')  
    if name == 'xgp' and password == '123.com':
        print('通过验证，即将登陆......')
        break
    else:
        count = count - 1
        print('还剩'+str(count)+"次机会")

Output (1):

请输入您的用户名：1
请输入您的密码：1
请输入您的用户名：1
请输入您的密码：1
请输入您的用户名：1
请输入您的密码：1
账号锁定

Output (2):

请输入您的用户名：xgp
请输入您的密码：123.com
登陆成功

Three, while the loop processing lists and dictionaries

The for loop is an effective way through the list, but in a for loop should not modify the list, otherwise it will lead to Python difficult to track its elements. To modify while traversing the list, you can use a while loop.

By the while loop combined with the use of lists and dictionaries, can collect, store and organize a lot of output, and display for later viewing.

1, similar to the copy list

users = ['alpha','byta','gima']
users_shadow = []

while users:
    current_user = users.pop()
    users_shadow.append(current_user)

print(users_shadow)

Output:

['gima', 'byta', 'alpha']

for replication cycle

for i in users:
    users_shdow.append(i)
print(users_shadow)

Output:

['gima', 'byta', 'alpha']

2, delete the specified list of elements among the

users = ['alpha','byta','gima']
print(users)
while 'byta' in users:
    users.remove('byta')
print(users)

Output:

['alpha', 'byta', 'gima']
['alpha', 'gima']

3. Create a survey program, each cycle when prompted to enter the name and answer the survey, the collected data will be stored in a dictionary

# 创建一个空字典
responses = {}

# 设置标志：表示调查是否继续
flag = True

# 循环操作
while flag:
    #提示输入接受调查的名字和回答
    name = input('请输入您的名字：')
    response = input('清输入您的答案：')

    # 将答案存储到字典中
    responses[name] = response

    # 是否还有人需要参加调查
    repeat = input('是否还有人需要参加调查：(yes/no)')
    if repeat == 'no':
        flag = False

# 显示调查结果
print('\n-------------------调查结果-------------------')
for name,response in responses.items():
    print(name + ">>>" + response)

Output:

请输入您的名字：wsd
清输入您的答案：123
是否还有人需要参加调查：(yes/no)yes
请输入您的名字：wushaox
清输入您的答案：x
是否还有人需要参加调查：(yes/no)no

-------------------调查结果-------------------
wsd>>>123
wushaox>>>x