Checking that user input is an int (python) [duplicate]

Question

Have been stuck on this for about an hour. Currently trying to teach myself Programming using Python. I am using a textbook for the programming stuff which walks me through pseudocode and then I attempt to convert this into python to learn the syntax. While to program runs and adds as it is supposed to, it will not print what I want it to if the user enters anything but an integer.

Pseudocode I am looking at:

1 Declare Count As Integer 2 Declare Sum As Integer 3 Declare Number As Float 4 Set Sum = 0 5 For (Count = 1; Count <=10; Count++) 6 Write “Enter an integer: “ 7 Input Number 8 If Number != Int(Number) Then 9 Write “Your entry is not an integer.” 10 Write “The summation has ended.” 11 Exit For 12 Else 13 Set Sum = Sum + Number 14 End If 15 End For 16 Write “The sum of your numbers is: “ + Sum

This is the code i have written to this point:

sum = 0 for count in range(0, 10): number = int(input("Write an integer: ")) if number != int(number): print ("Your entry is not an integer.") print ("The summation has ended.") break else: sum = sum + number continue print("The sum of your numbers is: " + str(sum))

this is meaningless: number != int(number) because you already assign to number the result from int(input(...)) which means it's always going to be an int — EdChum
– EdChum, Commented Nov 24, 2017 at 14:48
continue at the end is redundant. your loop will continue with or without that statement — Adelin
– Adelin, Commented Nov 24, 2017 at 14:50

Vyko · Accepted Answer · 2017-11-24 14:49:59Z

2

The int(arg) function throws an exception if arg is not an integer.

You need to catch the exception:

number = input() try: number = int(number) except ValueError: print "Number is not an integer"

answered Nov 24, 2017 at 14:49

Vyko

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3 Comments

Steve Byrne Over a year ago

Note you should credit your sources (stackoverflow.com/questions/5424716/…) and or at least add to them by noting that this works in Python 3, but Python 2 you should cast to a string first such as: int(str(number)) as @maxkoryukov noted in the above answer's comments.

Runferurlife Over a year ago

I see this.. where would I put it in the code I already have? I have seen this try-except method and attempted to put it into my code for about 30 min. Couldn't figure it out.

Runferurlife Over a year ago

after a little more research I understand what you are trying to say here. Thank you.

Alan Kavanagh · Accepted Answer · 2017-11-24 14:50:39Z

You could do something like this:

sum = 0 for count in range(1, 10): try: sum += int(input("Write an integer: ")) except ValueError: print("Your entry is not an integer.") print("The summation has ended.") break print("The sum of your numbers is: " + str(sum))

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