7.1 working principle of function input()
The function input() has a parameter, which can be displayed to the user for prompt; The function input() pauses the program and waits for the user to enter some text
message = input("Tell me something, and I will repeat it back to you:")
print(message)
'''
If you enter: Hello， everyone!
The screen also displays: Hello， everyone!
'''
7.1.1 write clear procedures
Tips and suggestions on function input()
- A space is included at the end of the prompt, so that the prompt information is separated from user input
- If the prompt information is too complex, it can be passed with a variable
prompt = "If you tell us who are you,we can personalize the message you see."
prompt += "\nWhat's your first name? "
name = input(prompt)
print(f"\nHello, {name}!")
'''
The code is executed as follows:
If you tell us who are you,we can personalize the message you see.
What's your first name? zhang xy
Hello, zhang xy!
'''
7.1.2 use input() to get numeric input
When using the function input(), the user input is parsed into a string. If you want to use an integer, you can use the function int()
age = input("How old are you? ")
print(type(age))
age = int(age)
print(type(age))
'''
Output:
How old are you? 18
<class 'str'>
<class 'int'>
'''
7.1.3 modulo operator
%Modulo two numbers and return the remainder, such as:
4% 3 returns 1
7.2 while loop
Both for and while statements are loops. For is generally used for traversal and while is generally used for continuous execution until the conditions are not met
7.2.1 using the while loop
current_number = 1
while current_number <= 5:
print(current_number)
current_number += 1
'''
Output:
1
2
3
4
5
'''
7.2.2 let the user choose when to exit
Define an exit value in the while loop to launch the loop program
prompt = "\nTell me something, and I will repeat it back to you:"
prompt += "\nEnter 'quit' to end the programe. "
message = ""
while message != 'quit':
message = input(prompt)
if message != 'quit':
print(message)
'''
Output:
Tell me something, and I will repeat it back to you:
Enter 'quit' to end the programe. hello world
hello world
Tell me something, and I will repeat it back to you:
Enter 'quit' to end the programe. 123
123
Tell me something, and I will repeat it back to you:
Enter 'quit' to end the programe. quit
'''
7.2.3 use signs
If there are more than one exit condition, if the exit condition is set as in the previous program, the inspection condition will be complex and difficult. At this time, the flag bit can be used (the inspection and change of the flag bit can be placed elsewhere)
prompt = "\nTell me something, and I will repeat it back to you:"
prompt += "\nEnter 'quit' to end the programe. "
active = True
while active:
message = input(prompt)
if message == 'quit':
active = False
else:
print(message)
'''
Output:
Tell me something, and I will repeat it back to you:
Enter 'quit' to end the programe. hello
hello
Tell me something, and I will repeat it back to you:
Enter 'quit' to end the programe. 123
123
Tell me something, and I will repeat it back to you:
Enter 'quit' to end the programe. quit
'''
7.2.4 using break to exit the loop
Use the break statement to exit the loop immediately without executing all the remaining code in the loop
prompt = "\nTell me something, and I will repeat it back to you:"
prompt += "\nEnter 'quit' to end the programe. "
while True:
message = input(prompt)
if message == 'quit':
break
else:
print(message)
'''
Output:
Tell me something, and I will repeat it back to you:
Enter 'quit' to end the programe. hello
hello
Tell me something, and I will repeat it back to you:
Enter 'quit' to end the programe. 123
123
Tell me something, and I will repeat it back to you:
Enter 'quit' to end the programe. quit
'''
7.2.5 using the continue statement in a loop
The continue statement will exit this cycle and will not execute the rest of the code in this cycle. Note the difference between the continue statement and the break statement
# Use continue to exit this cycle
current_number = 0
while current_number < 10:
current_number += 1
if current_number % 2 == 0:
continue
print(current_number)
'''
Output:
1
3
5
7
9
'''
# Use break to exit the loop
current_number = 0
while current_number < 10:
current_number += 1
if current_number % 2 == 0:
break
print(current_number)
'''
Output:
1
'''
7.2.6 avoid infinite cycles
The while loop must have explicit exit conditions, or the program will execute endlessly
7.3 using the while loop to process lists and dictionaries
For loop is an effective way to traverse the list, but the list should not be modified in the for loop, otherwise it will be difficult to track the elements in it; To modify the list while traversing it, you can use the while loop
7.3.1 moving elements between lists
There are newly registered but unauthenticated users in a list. After user authentication, move the user to the authenticated user list
unconfirmed_users = ['alice', 'brian', 'candace']
confirmed_users = []
while unconfirmed_users:
confirmed_user = unconfirmed_users.pop()
print(f"Verifying user:{confirmed_user.title()}")
confirmed_users.append(confirmed_user)
print("\nThe following users have been confirmed:")
for confirmed_user in confirmed_users:
print(confirmed_user.title())
'''
Output:
Verifying user:Candace
Verifying user:Brian
Verifying user:Alice
The following users have been confirmed:
Candace
Brian
Alice
'''
7.3.2 delete all list elements with specific values
pets = ['dog', 'cat', 'dog', 'goldfish', 'cat', 'rabbit', 'cat']
print(pets)
while 'cat' in pets:
pets.remove('cat')
print(pets)
'''
Output:
['dog', 'cat', 'dog', 'goldfish', 'cat', 'rabbit', 'cat']
['dog', 'dog', 'goldfish', 'rabbit']
'''
7.3.3 use user input to populate the dictionary
You can use the while loop to store what someone says in a dictionary
responses = {}
polling_active = True
while polling_active:
name = input("\nWhat's your name? ")
response = input("What would you want to say? ")
responses[name] = response # Store sb's words in a dictionary
repeat = input("Any one else?('yes' or 'no') ")
if repeat == 'no':
polling_active = False
print(responses)
print(f"\n{'Poll Result':=^40}")
for name,response in responses.items():
print(f"{name} says: {response}.")
'''
Output:
What's your name? zhang xy
What would you want to say? python would change world
Any one else?('yes' or 'no') yes
What's your name? mao
What would you want to say? good good study, day day up
Any one else?('yes' or 'no') no
{'zhang xy': 'python would change world', 'mao': 'good good study, day day up'}
==============Poll Result===============
zhang xy says: python would change world.
mao says: good good study, day day up.
'''
7.4 summary
slightly