tkinter: assigning multiple functions to one button

Question

I am trying to construct a Roman numeral converter using Tkinter. I need to use one button which will convert decimals to Roman numerals if numbers are entered, and Roman numerals to decimals if numerals are entered. How do I assign the two functions to one button, and call whichever function corresponds to what is entered?

This is what I have so far:

    from tkinter import *
    root = Tk()
    root.title('Roman numerals')
    root.geometry('400x300')

    numRomanMap = (('M',  1000), ('CM', 900), ('D',  500), ('CD', 400), ('C',  100), ('XC', 90), ('L',  50), ('XL', 40), ('X',  10), ('IX', 9), ('V',  5), ('IV', 4), ('I',  1))

    def roman_number():
        roman_string = ''
        n = float(eval(ent.get()))
        wrongValue = ('Number is out of range')
        if not 1 <= n <= 9999:
                    return wrongValue
        for numeral, integer in numRomanMap:
            while n >= integer:
                roman_string += numeral
                n -= integer
        print (roman_string)

    def decimal_number(s):
        dec_number = 0
        s = str(eval(ent.get()))
        index = []
        for i in range(len(s)):
            for numeral, integer in numRomanMap:
                if s[i] == numeral:
                    index.append(integer)
        index.append(0)
        for i in range(len(s)):
            if index[i] >= index[i+1]:
                dec_number = dec_number + index[i]
            else:
                dec_number = dec_number - index[i]
        print (dec_number)

    Convertb = Button(root, text='Convert', command = roman_number)
    ent = Entry(root)
    ent.pack()
    ent.delete(0, END)
    ent.insert(0, 'Enter a number')
    Convertb.pack()

    root.mainloop()

could make a function which simply checks the input of the user, and then that branches off into two other functions, one for decimal input and the other for RN input — Goralight
– Goralight, Commented Oct 20, 2017 at 10:08

Avión · Accepted Answer · 2017-10-20 10:18:24Z

1

Add a function to see if the input is a number.

def check_input():
    s = ent.get()
    if (isinstance(s, int)):
        roman_number(s)
    else:
        decimal_number(s)

And call that function from the button:

Convertb = Button(root, text='Convert', command = check_input)

answered Oct 20, 2017 at 10:18

Avión

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5 Comments

Goralight Over a year ago

Does tkinters entry.get() return int if its get is only int? or does it always, no matter the input, grab the input as a str?

j_4321 Over a year ago

@Goralight entry.get() always returns a string, so you can use something like s.isdigit() to check the input.

Greta Over a year ago

@Avión Thanks for your answer. I'm receiving the following error messages: line 40, in check_input decimal_number(n) line 29, in decimal_number if index[i] >= index[i+1]: IndexError: list index out of range

Avión Over a year ago

@Greta That's a problem with your decimal_number function, not with the question you stated on the post.

Avión Over a year ago

Glad No problem, @Greta . If it helped, please, tick the answer. Thank you!

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