Dictionary in Python - checking for key

Question

Here is the code that I wrote so far:

def Ordinal(check):
    data={1:"First", 2:"Second", 3:"Third", 4:"Fourth", 5:"Fifth", 6:"Sixth", 7:"Seventh", 8:"Eighth", 9:"Ninth", 10:"Tenth", 11:"Eleventh", 12:"Twelfth"}

    if check in dict.keys: 
        return dict.get(check)
    else:
        return""
def main():
    Num=input("Enter a number (1-12) to get its ordinal: ")
    print ("The ordinal is", Ordinal(Num))
main()          

The program is suppose to get a number between 1 to 12 from the user and then print its ordinal. I am having trouble using the input and checking to see if it is a key and then returning its value as a print statement in the main function. The error is related to the if statement.

Answer 1

Try this ...

def Ordinal(check):
    data={1:"First", 2:"Second", 3:"Third", 4:"Fourth", 5:"Fifth", 6:"Sixth", 7:"Seventh", 8:"Eighth", 9:"Ninth", 10:"Tenth", 11:"Eleventh", 12:"Twelfth"}
    return data.get(int(check), "")

def main():
    Num=input("Enter a number (1-12) to get its ordinal: ")
    print ("The ordinal is", Ordinal(Num))
main()

The if check is not necessary since dict.get can return a default value.

Answer 2

Your problem is with if check in data.keys: because:

data.keys is a method: <built-in method keys of dict object at 0x10b989280>

You should call the method data.keys() which returns [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]

Or you can do:

def Ordinal(check):
    data={1:"First", 2:"Second", 3:"Third", 4:"Fourth", 5:"Fifth", 6:"Sixth", 7:"Seventh", 8:"Eighth", 9:"Ninth", 10:"Tenth", 11:"Eleventh", 12:"Twelfth"}

    if check in data:
        return data.get(check)
    else:
        return""
def main():
    Num=input("Enter a number (1-12) to get its ordinal: ")
    print ("The ordinal is", Ordinal(Num))
main()

Or as @astrosyam pointed out, using data.get(int(check), "") is a cleaner way.

Answer 3

To add to Bryan Oakley's answer you can do the following:

def Ordinal(check):
    data={1:"First", 2:"Second", 3:"Third", 4:"Fourth", 5:"Fifth", 6:"Sixth", 7:"Seventh", 8:"Eighth", 9:"Ninth", 10:"Tenth", 11:"Eleventh", 12:"Twelfth"}

    if check in data:
        return data.get(check)
    else:
        return""
def main():
    Num=eval(input("Enter a number (1-12) to get its ordinal: ")) #notice eval here!
    print ("The ordinal is", Ordinal(Num))
main()

Notice that I added the eval by the input line.

Answer 4

Maybe something like this? Don't print the output if they input an invalid key.

data = {
    1: "First", 2: "Second", 3: "Third", 4: "Fourth", 5: "Fifth",
    6: "Sixth", 7: "Seventh", 8: "Eighth", 9: "Ninth", 10: "Tenth",
    11: "Eleventh", 12: "Twelfth"}


def Ordinal(check):
    return data[check]


def main():
    Num = input("Enter a number (1-12) to get its ordinal: ")

    try:
        print ("The ordinal is {}".format(Ordinal(int(Num))))
    except ValueError:
        print("didnt enter a valid integer")
    except KeyError:
        print("Not number between 1-12")

main()

If using python 2.x use raw_input instead of input .