Restrict inputs to only integer in python and display error message

Question

I have multiple inputs here but I want to restrict the input to only integers and display an error message when user inputs a character other than input. And keep asking the user to input the right value before going to the next item.Here is my code:

print ("welkom bij de munten teller")

cent= int(input("vul het aantal 1 centjes in: "))
stuiver= int(input("vul het aantal stuivers in: "))
dubbeltje= int(input("vul het aantal dubbeltjes in: "))
kwartje= int(input("vul het aantal kwartjes in: "))
SRD= int(input("vul het aantal 1 SRD's in: "))
dalla= int(input("vul het aantal 2,50's in: "))

totaal = int ()

fin_cent= cent * 0.01
fin_stuiver = stuiver* 0.05
fin_dubbeltje = dubbeltje * 0.10
fin_kwartje = kwartje * 0.25
fin_SRD = SRD*1
fin_dalla = dalla * 2.50

totaal = fin_cent + fin_stuiver + fin_dubbeltje + fin_kwartje + fin_SRD + fin_dalla
print ("Het totaal is: ", totaal)
#print (totaal)

input("Druk op enter om het programma te beindigen;)")

Patrick Haugh · Accepted Answer · 2018-01-19 02:38:41Z

3

You have three basic options:

Attempt to convert the input to an integer and let any errors raised propagate naturally. The user will be shown a ValueError: invalid literal for int() with base 10: <your input>
```
value = int(input('...'))
```
Wrap the code that may raise an exception in a try..except block. This allows you to catch the error and raise your own.
```
try:
    value = int(input('...'))
except ValueError:
    raise ValueError('Make sure you input integers')
```

Wrap that try block in a loop, so it keeps asking until it gets a correct input

while True:
    try:
        value = int(input('...'))
    except ValueError:
        print('Please enter a valid integer')
        continue
    break

answered Jan 19, 2018 at 2:38

Patrick Haugh

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Comments

thuyein · Accepted Answer · 2018-01-19 02:38:40Z

1

cent= getInt("vul het aantal 1 centjes in: ")
stuiver= getInt("vul het aantal stuivers in: ")

def getInt(msg):
    var = input(msg)
    if not var.isdigit():
        print("Number Only")
        exit()
    return int(var)

You have to accept them as string first. Then check if they're digit or not using .isdigit() function. Since you have a lot of inputs, creating a function is easier.

answered Jan 19, 2018 at 2:38

thuyein

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