Can you have different validatecommand for different entry widgets?

Question

In sir Bryan Oakley's detailed answer for validating Entry widget in the post Interactively validating Entry widget content in tkinter, the vcmd is defined as:

 vcmd = (self.register(self.onValidate),
            '%d', '%i', '%P', '%s', '%S', '%v', '%V', '%W')
    self.entry = tk.Entry(self, validate="key", validatecommand=vcmd)

with 'self' being (presumably) the class object. So I'm just wondering if it is possible to have different type of validatecommand for different entry widgets, because what I'm doing now:

vcmd = (self.register(self.onValidate), '%P', '%S')
vcmd1 = (self.register(self.onValidate1), '%P', '%S')
vcmd2 = (self.register(self.onValidate2), '%P', '%S')

is just redefining instead creating new validatecommand, and the first onValidate is just ignored. What could I do?

EDIT: What I've tried so far

from tkinter import *
import math
from tkinter import messagebox


class TimeGenerator:

    def __init__(self,master):
        frame = Frame(master)
        frame.grid()
        label_iso = Label(root, text="Isotope A, Element")
        label_vol = Label(root, text="Voltage")
        label_range = Label(root, text="Charge Range")

        def _register(self, func, subst=None, needcleanup=1):
            f = CallWrapper(func, subst, self).__call__
            name = repr(id(f))
            try:
                func = func.im_func
            except AttributeError:
                pass
            try:
                name = name + func.__name__
            except AttributeError:
                pass
            self.tk.createcommand(name,f)
            if needcleanup:
                if self._tclCommands is None:
                    self._tclCommands = []
                self.tclCommands.append(name)
            return name
        register = _register

        vcmd = (self.register(self.onValidate), '%P', '%S')
        vcmd1 = (self.register(self.onValidate1), '%P', '%S')
        vcmd2 = (self.register(self.onValidate2), '%P', '%S')

        entry_iso = Entry(self,validate="key", validatecommand=vcmd)
        entry_vol = Entry(self,validate="key", validatecommand=vcmd1)
        entry_range = Entry(self,validate="key",validatecommand=vcmd2)

        def onValidate(self, P, S):
            validString = 'qwertyuiopasdfghjklzxcvbnmQWERTYUIOPASDFGHJKLZXCVBNM,1234567890'
            if not S in validString:
                return False
            if str.__contains__(',', P):
                if len(P.split(",")) >= 2:
                    return False
                messagebox.showinfo("Error", "Expected Form: ex. 133,Cs")
            return True

        label_iso.grid(row=0, sticky=E)
        label_vol.grid(row=1, sticky=E)
        label_range.grid(row=2, sticky=E)

        entry_iso.grid(row=0, column=1)
        entry_vol.grid(row=1, column=1)
        entry_range.grid(row=2,column=1)

        button = Button(root, text='Time Range', command=self.calculateTime)
        button.grid(row=3, columnspan=2)

        self.text = Text(root)
        self.iso = entry_iso
        self.vol = entry_vol
        self.r = entry_range

    def calculateTime(self):
        x = 5
        if self.r.get() == "" or self.iso.get() == "" or self.vol.get() == "":
            messagebox.showinfo("Error", "No field can be empty")

        self.iso = self.iso.get().replace(" ", "")
        list = []
        for e in self.iso.split(","):
            list.append(e)

        f = open("/Users/LazyLinh/PycharmProjects/mass.mas12.txt", "r")
        i = 0
        while (i < 40):
            header = f.readline()
            i += 1
        self.mass = 0

        for line in f:
            line = line.strip()
            columns = line.split()
            if (list[0] == columns[3]):
                if (list[1].lower() == columns[4].lower()):
                    if (len(columns) == 16):
                        self.mass = float(columns[13].replace("#","")) + float(columns[14].replace("#",""))
                    else:
                        self.mass = float(columns[12].replace("#","")) + float(columns[13].replace("#",""))

        self.r = self.r.get().replace(" ", "")
        tup = tuple(int(x) for x in self.r.split(","))

        list = []
        for q in range(tup[0], tup[1] + 1):
            y = x * math.sqrt(self.mass / (2 * q * float(self.vol.get())))
            list.append(y)
        i = tup[0]
        for time in list:
            self.text.insert("end", "%d: %s\n" % (i, time))
            i = i + 1
        self.text.pack()

root = Tk()
b = TimeGenerator(root)
root.mainloop()

Answer 1

From the sources:

(File Tkinter.py, class Misc)

def _register(self, func, subst=None, needcleanup=1):
    """Return a newly created Tcl function. If this
       function is called, the Python function FUNC will
       be executed. An optional function SUBST can
       be given which will be executed before FUNC."""
    f = CallWrapper(func, subst, self).__call__
    name = repr(id(f))
    try:
        func = func.im_func
    except AttributeError:
        pass
    try:
        name = name + func.__name__
    except AttributeError:
        pass
    self.tk.createcommand(name, f)
    if needcleanup:
        if self._tclCommands is None:
            self._tclCommands = []
        self._tclCommands.append(name)
    return name
register = _register

The most important line from the above code for your question:

self._tclCommands.append(name)

This means that each time you register a new callback, the function is registered as a completely different callback, so you do have a new validatecommand.

You can also add different parameters to them.

Edit 1

python 3:

in /lib/tkinter/__init__.py the source code for register is the same, so the functionality is still the same.

What issues exactly do you encounter?

Edit 2

the code i posted is not meant to be implemented into your code. It shows the implementation inside the tkinter libraries.

Your issue is that your class is not derived from a tkinter based class like tkinter.Frame, tkinter.Toplevel or tkinter.Tk.

Only tkinter derived classes can use self.register. Do not implement the function inside your code.

If you would have a class derived from tkinter it would work.

Example:

import tkinter
class MyClass(tkinter.Frame):
    def __init__(self, *args, **kwargs):
        tkinter.Frame.__init__(self, *args, **kwargs)

        vmcd1 = (self.register(self.__vcmd1), '%P', '%S')
        vmcd2 = (self.register(self.__vcmd2), '%P', '%S')
        vmcd3 = (self.register(self.__vcmd3), '%P', '%S')

        entry1 = tkinter.Entry(self, validate="key", validatecommand=vcmd1)
        entry2 = tkinter.Entry(self, validate="key", validatecommand=vcmd2)
        entry3 = tkinter.Entry(self, validate="key", validatecommand=vcmd3)

        entry1.grid()
        entry2.grid()
        entry3.grid()


    def __vcmd1(self, P, S):
        print("__vcmd1")

    def __vcmd2(self, P, S):
        print("__vcmd2")

    def __vcmd2(self, P, S):
        print("__vcmd2")

This is how you would set sth. like this up. Also, your definition of functions would not be matching as self.function_name only works is inside your class, not inside a class method.