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About quitting the factorial program in an endless loop [duplicate]

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Asking the user for input until they give a valid response
(22 answers)
Closed 2 years ago.
My goal is creating a factorial program in python that asks infinite user input to find factorial of the number user type, until I would like to quit the program. But there is probably discrepancy between the lines of the code to works for exit the program and integer numbers below it.
1) I tried to solve this to not write int(input) I wrote just
input('Enter a number. Type exit to stop:> ')
both above or below the while True statement but it didn't work.
2) I also want to use lower() function to quit the program but when I use it, the discrepancy happens again because I ask user input for an integer but when I turn it to a normal input and type it the above while True statement, problem occurs.
3) Also I want to user input as a number with using that isdigit() function tried to use like this but it didn't work well:
factorial = 1
user_input = input('Enter a number: ')
while user_input.lower() != 'exit':
while not user_input.isdigit():
print('This is not a number. Please try again:> ')
user_input = int(input('Try again:> '))
user_input = int(input('Enter a new number: '))
.
.
.
and this, too didn't work
My actual code is this:
while True:
factorial = 1
user_input = int(input('Enter a number. Type exit to stop:> '))
if user_input == 'exit':
print('You are quitting the program')
break
elif user_input < 0:
print("Sorry, factorial does not exist for negative numbers")
elif user_input == 0:
print("The factorial of 0 is 1")
else:
for i in range(1, user_input + 1):
factorial = factorial * i
print("The factorial of", user_input, "is", factorial)
The program works like this:
Enter a number. Type exit to stop:> 4
The factorial of 4 is 24
Enter a number. Type exit to stop:> 5
The factorial of 5 is 120
Enter a number. Type exit to stop:> 6
The factorial of 6 is 720
and when I type 'exit' to quit from program I am receiving this kind of error:
Traceback (most recent call last):
File "E:/Kodlar/Python/Taslak projeler/taslak177.py", line 5, in <module>
user_input = int(input('Enter a number. Type exit to stop:> '))
ValueError: invalid literal for int() with base 10: 'exit'
As you can see, code blocks work instead of quitting the program with user input. How can I fix this?
Can anyone help? Thanks already!
Edit: I reorganized the code and it works perfectly fine. Thanks for your all responses!
while True:
user_input = input("Enter a number:> ")
if user_input == "exit":
print('You are quitting the program...')
break
else:
try:
factorial = 1
user_input = int(user_input)
if user_input < 0:
print("Sorry, factorial does not exist for negative numbers")
elif user_input == 0:
print("The factorial of 0 is 1")
else:
for i in range(1, user_input + 1):
factorial = factorial * i
print(f'The factorial of {user_input} is {factorial}')
except ValueError:
print("Please provide a valid number")

You should check if the input is exit before converting it to int and if so, break the loop.
Try this instead:
while True:
user_input = input("Enter a number:")
if user_input == "exit":
print('You are quitting the program')
break
else:
try:
user_number = int(user_input)
if user_number < 0:
print("Sorry, factorial does not exist for negative numbers")
elif user_number == 0:
print("The factorial of 0 is 1")
else:
# calc factorial here
except ValueError:
print("Please provide a valid number")

Your program get int inputs,
user_input = int(input('Enter a new number: '))
try this instead, get string input
user_input = input('Enter a new number: ')
and convert it into int later
user_input = int(user_input)

Because you are casting the user's response (a string) into an int in both cases.
user_input = int(input('Enter a new number: '))
and later
user_input = int(input('Enter a number. Type exit to stop:> '))
Perhaps try a little tweak:
while True:
factorial = 1
user_input = input('Enter a number. Type exit to stop:> ')
if user_input.lower().strip() == 'exit':
print('You are quitting the program')
break
elif user_input.isnumeric() and user_input < 0:
print("Sorry, factorial does not exist for negative numbers")
elif user_input.isnumeric() and user_input == 0:
print("The factorial of 0 is 1")
elif user_input.isnumeric():
for i in range(1, user_input + 1):
factorial = factorial * i
print("The factorial of", user_input, "is", factorial)
else:
print("Please enter an integer or 'exit'")
You could also wrap another if so you don't duplicate the isnumeric() tests

Passing 'ValueError' & 'continue' in a function and call it

I am trying to check user inputs to ensure that:
1) It is a floating number
2) Floating number is not negative
I am trying to put above 2 checks into a function and call it after user has input into a variable.
However, I cant seem to put 'ValueError' & 'continue' in a function that I can call. Is this possible?
I have tried below code, but it repeats from the top when I key in 't' for salCredit, or any of the next few variables. The code will work if I were to repeat 'ValueError' & 'continue' for every variable. I'm just wondering if there is a shorter way of doing do?
def interestCalculator():
#User inputs required for calculation of interest earned.
while True:
try:
mul_AccBal = float(input("Enter your Account Balance: "))
#checkInputError(accBal)
salCredit = float(input("Enter your Salary: "))
#checkInputError(salCredit)
creditCard = float(input("Credit Card Spend (S$): "))
#checkInputError(creditCard)
except ValueError:
print("Please enter a valid number.")
continue
def checkInputError(userInput):
if userInput < 0:
print("Please enter a positive number.")
interestCalculator()
Expected results:
Scenario 1: if user inputs 't'
Enter your Account Balance: 5000
Enter your Salary: t
Please enter a valid number.
Enter your Salary: 500
Scenario 2: if user inputs negative number
Enter your Account Balance: 5000
Enter your Salary: -50
Please enter a valid number.
Enter your Salary: 500
Current results:
Scenario 1: if user inputs 't'
Enter your Account Balance: 5000
Enter your Salary: t
Please enter a valid number.
Enter your Account Balance:
Scenario 2: if user inputs negative number
Enter your Account Balance: 5000
Enter your Salary: -50
Please enter a positive number.
Credit Card Spend (S$):

You could create a function that continues prompting for input until a valid float is input
def get_float_input(prompt):
while True:
try:
user_input = float(input(prompt))
if user_input < 0:
print("Please enter a positive number.")
continue # start the while loop again
return user_input # return will break out of the while loop
except ValueError:
print("Please enter a valid number.")
mul_AccBal = get_float_input("Enter your Account Balance: ")
salCredit = get_float_input("Enter your Salary: ")
creditCard = get_float_input("Credit Card Spend (S$): ")

Try this:
def interestCalculator():
#User inputs required for calculation of interest earned.
while True:
invalid = True
while invalid:
try:
mul_AccBal = float(input("Enter your Account Balance: "))
invalid=checkInputError(salCredit)
except ValueError:
print("Please enter a valid number.")
continue
invalid = True
while invalid:
try:
salCredit = float(input("Enter your Salary: "))
invalid=checkInputError(salCredit)
except ValueError:
print("Please enter a valid number.")
continue
invalid = True
while invalid:
try:
creditCard = float(input("Credit Card Spend (S$): "))
invalid=checkInputError(salCredit)
except ValueError:
print("Please enter a valid number.")
continue
def checkInputError(userInput):
if userInput < 0:
print("Please enter a positive number.")
return True
return False
interestCalculator()

you need to break you while loop if all the input is successful (also note that the continue at the end of the while loop is unnecessary). and if you want to have a validation for every number separately, you could do something like this:
def get_float(message, retry_message="Please enter a valid number."):
while True:
try:
ret = float(input(message))
if ret >= 0:
return ret
else:
print(retry_message)
except ValueError:
print(retry_message)
def interestCalculator():
mul_AccBal = get_float("Enter your Account Balance: ")
salCredit = get_float("Enter your Salary: ")
creditCard = get_float("Credit Card Spend (S$): ")

Crashing when improper input given more than once

I'm trying to make a simple number guesser program, it works pretty well however if I enter 'a' twice instead of a valid int it crashes out. Can someone explain what I'm doing wrong here.
import random
def input_sanitiser():
guess = input("Please enter a number between 1 and 10: ")
while True:
if type(guess) != int:
guess = int(input("That isn't a number, try again: "))
elif guess not in range (1,11):
guess = int(input("This is not a valid number, try again: "))
else:
break
def main():
number = random.randrange(1,10)
guess = 0
input_sanitiser()
while guess != number:
if guess < number:
print("This number is too low!")
input_sanitiser()
if guess > number:
print("This number is too high!")
input_sanitiser()
else:
break
print ("Congratulations, you've guessed correctly")
if __name__ == "__main__":
main()

You want to check the input before trying to convert it to int:
int(input("This is not a valid number, try again: "))
I would write:
while True:
try:
guess = int(input("This is not a valid number, try again: "))
except ValueError:
pass
else:
break
Side note: the code isn't working as expected:
def main():
number = random.randrange(1,10)
guess = 0
input_sanitiser() # <<<<<<<<<<
while guess != number:
Note that input_sanitiser does not modify the variable guess in main, you need some other way round, like processing the input then returning the result from input_sanitiser, like this:
def input_sanitiser():
guess = input("Please enter a number between 1 and 10: ")
while True:
try:
guess = int(input("This is not a valid number, try again: "))
except ValueError:
continue # keep asking for a valid number
if guess not in range(1, 11):
print("number out of range")
continue
break
return guess
def main():
number = random.randrange(1,10)
guess = input_sanitiser()
while guess != number:
if guess < number:
print("This number is too low!")
guess = input_sanitiser()
if guess > number:
print("This number is too high!")
guess = input_sanitiser()
else:
break
print ("Congratulations, you've guessed correctly")

Not sure what is wrong with this code for Python for Everybody 5.2

I'm taking Coursera and doing a python course.
I'm struggling with the last assignment.
Here is the assignment:
5.2 Write a program that repeatedly prompts a user for integer numbers until the user enters 'done'. Once 'done' is entered, print out the largest and smallest of the numbers. If the user enters anything other than a valid number catch it with a try/except and put out an appropriate message and ignore the number. Enter 7, 2, bob, 10, and 4 and match the output below.
My code:
# largest = None
# smallest = None
store=[]
while True:
s = input("Enter a number: ")
if s == "done":
break
try:
store.append(int(s))
except:
print("Invalid input")
largest = max(store)
smallest = min(store)
# print("Invalid input")
print("Maximum is ",largest)
print("Minimum is ",smallest)
Please help.
Thanks

store=[]
while True:
s = input("Enter a number: ")
if s == "done":
break
try:
store.append(int(s))
except:
print("Invalid input")
largest = max(store)
smallest = min(store)
print("Maximum is ",largest)
print("Minimum is ",smallest)

Python Nested Loop Enter Value and Confirm Answer

I'm trying to write a simple block of code that has a user enter an interest rate. The number must be 0 or greater, any other value will be rejected, the user must be polled until a valid number is input. If the number is greater than 10%, the user must be asked if he/she really expects an interest rate that high, if the user replies in the affirmative, the number is to be used, otherwise the user will be asked to input the value again and the above checks will be made. I'm having trouble understanding the nested loop aspect of this. Any help is greatly appreciated!
def main():
while True:
try:
interest_rate = int(input("Please enter an interest rate: "))
except ValueErrror:
print("Entered value is not a number! ")
except KeyboardInterrupt:
print("Command Error!")
else:
if 0 <= interest_rate < 10:
break
elif interest_rate > 10:
print("Entered interest rate is greater than 10%. Are you sure? (y/n): ")
main()

do it all in the try, if inp > 10, ask if the user is happy and break if they are, elif user input is within threshold just break the loop:
def main():
while True:
try:
interest_rate = int(input("Please enter an interest rate: "))
if interest_rate > 10:
confirm = input("Entered interest rate is greater than 10%. Are you sure? (y/n): ")
if confirm =="y":
break
elif 0 <= interest_rate < 10:
break
except ValueError:
print("Entered value is not a number! ")
return interest_rate
main()

Three things jump out:
1) ValueErrror should be ValueError
2) You don't handle the user input on the final test
3) You probably want to change the < 10 to be <= 10

else:
if 0 <= interest_rate < 10:
break
elif interest_rate > 10:
print("Entered interest rate is greater than 10%. Are you sure? (y/n): ")
can be:
if 0 <= interest_rate <= 10:
break
print("Entered interest rate is greater than 10%. Are you sure? (y/n): ")
except the last line must take the response and process it.
Your else was not related to an if
Your elif was unnecessary after break

Make the print("Entered interest rate is greater than 10%. Are you sure? (y/n): ") an input
answer = int(input("Are you sure?"))
if answer == "y":
break

I usually prefer to break down the solution and validation into different modules. Please check the below code to see how I break them down. So it is easy when it comes to debugging and testing.
def validating_user_input(num):
"""
"""
return num > 0
def getting_user_input():
"""
"""
user_input = int(raw_input("Enter the number that is greater than 0: "))
return user_input
def confirming_choose():
"""
"""
try:
user_choose = int(raw_input("Can you confirm your input? [0|1]? "))
except ValueError:
return False
return user_choose == 1
def main():
"""
"""
initial_cond = True
while initial_cond:
user_input = getting_user_input()
if validating_user_input(user_input):
if user_input > 10:
confirmation = confirming_choose()
while not confirmation:
getting_user_input()
#do you operating here
initial_cond = False
else:
print "It is not valid input."
if __name__ == "__main__":
main()