How to use numbers as variable name, or use a dict instead?

Question

I'm writing the program for a psychology experiment that requires participants to learn a new number pad mapping.

If the keys were letters it would be easy enough: a=1 , b=2 , c=3 etc.

But apparently Python doesn't allow mapping to integers. Hmm.

A partial solution could be to use a dictionary, such as:

newdict = {'1': 9, '2': 8, '3': 7}

However, participants will be typing into a text box, and when their entry appears in the box it needs to have been converted already. There is no clear way to apply the newdict['1'] call.

How can this remapping be accomplished?

Answer 1

Your instinct to use a dict is good -- it's an easy way to create a mapping from one character to another. You could also just use a list of tuples (eg: ((1, 9), (2, 8), ...) )

You don't mention the GUI toolkit (or whether you're just doing a console app), so I'll give a tkinter example to illustrate how to set up a key binding for each key using the dictionary. Using a tuple would be nearly identical.

import tkinter as tk # for python 2 use 'Tkinter'

class Example(tk.Frame):
    keymap = {'1': '9', '2': '8', '3': '7',
              '4': '6', '5': '5', '6': '4',
              '7': '3', '8': '2', '9': '1'}

    def __init__(self, parent):
        tk.Frame.__init__(self, parent)

        self.entry = tk.Entry(self, width=20)
        self.entry.pack(fill="x", pady=20, padx=20)

        for old_key, replacement in self.keymap.items():
            self.entry.bind('<KeyPress-%s>' % old_key,
                            lambda event, char=replacement: self.insert(char))

    def insert(self, char):
        self.entry.insert("insert", char)
        return "break"

if __name__ == "__main__":
    root = tk.Tk()
    Example(root).pack(fill="both", expand=True)
    root.mainloop()