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Most programs are designed to solve the end user’s problem, and to do so usually requires obtaining some information from the user. To do this, you will use the function input(). How to keep the program running so that users can input information as needed and use it in the program. You can use a while loop to keep the program running until the specified condition is not met.
functioninput()
The working principle of
- function
input()
Let the program pause and wait for the user to enter some text. - After taking user input, Python assigns it to a variable that you can use easily.
message = input("Tell me something, and I will repeat it back to you:")
print(message)
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- function
input()
Accept a parameter — a prompt or instruction to display to the user so that the user knows what to do.
Write clear programs
- Whenever I use a function
input()
You should specify clear, easy-to-understand prompts that specify exactly what information you want the user to provide. - By including a space at the end of the prompt (in this case, after a colon), you separate the prompt from the user’s input and let the user know exactly where his input began.
name = input("Please input your name: ")
print(f"Hello, {name}!")
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- Sometimes, the prompt can be longer than one line.
- In this case, the prompt can be assigned to a variable, which can then be passed to the function
input()
. That way, even if the prompt is more than one line,input()
Statements will also be very clear.
prompt = 'If you tell us who you are, we can personalize the messages you see.'
prompt += '\nWhat is your first name? '
name = input(prompt)
print(f"Hello, {name}!")
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useint()
To get numeric input
- Using the function
input()
Python interprets user input as a string. - function
int()
Converts a string representation of a number to a numeric representation.
age = input("How old are you? ")
age = int(age)
print(age > 18)
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- Be sure to convert numeric input to numeric representation before using it for calculation and comparison.
while
cycle
for
Loops are used to execute a code block for each element in the collection, whilewhile
The loop keeps running until the specified condition is not met.
usewhile
cycle
current_number = 1
while current_number <= 5:
print(current_number)
current_number += 1
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Let the user choose when to quit
- You can use a while loop to keep the program running as long as the user wants.
prompt = "Tell me something, and I will repeat it back to you:"
prompt += '\nEnter "quit" to end the program. '
message = ""
whilemessage ! ='quit':
message = input(prompt)
ifmessage ! ='quit':
print(message)
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Use sign
- Set the variable active to
True
To make the program initially active.
prompt = "Tell me something, and I will repeat it back to you:"
prompt += '\nEnter "quit" to end the program. '
active = True
while active:
message = input(prompt)
if message == 'quit':
active = False
else:
print(message)
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usebreak
Exit the loop
- Exit immediately
while
Loop, which no longer runs the rest of the code in the loop, regardless of the result of the conditional test, can be usedbreak
Statements.
prompt = 'Please enter the name of a city you have visited:'
prompt += '\n(Enter "quit" when you are finished.) '
while True:
city = input(prompt)
if city == 'quit':
break
else:
print(f"I'd love to go to {city.title()}!")
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Use in a loopcontinue
current_number = 0
while current_number < 10:
current_number += 1
if current_number % 2= =0:
continue
print(current_number)
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Avoid infinite loops
- each
while
Loops must have a way of stopping so they don’t go on forever.