steve wrote:
> for determine the maximum number of characters in an entry
>
> I have read several interpretations for the solution of the problem, but
> I wanted to find an alternative way (for convenience of the code)
>
> I kindly ask for an opinion on the use of validation in this way.
>
> -----
>
> problem: limit number of characters in different entries of a form.
>
> code:
>
> #!/usr/bin/python
> # -*- coding: utf-8 -*
>
> from Tkinter import *
>
>
> class View():
>
> def __init__(self, parent):
> self.parent = parent
> self.make_ui()
>
> def make_ui(self):
> ''' create user interface '''
> self.id_entry = Entry(self.parent, width=6)
> # take out the properties for understanding
>
> vcmd = (self.parent.register(self.maxlength_validate), '%P', 4)
> # 4 is my question
>
> self.id_entry.configure(validate="key", validatecommand=vcmd)
> self.id_entry.pack()
>
> self.name_entry = Entry(self.parent, width=30)
> # take out the properties for understanding
>
> vcmd = (self.parent.register(self.maxlength_validate), '%P', 20)
> # 20 is my question
>
> self.name_entry.configure(validate="key", validatecommand=vcmd)
> self.name_entry.pack()
>
> def maxlength_validate(self, value, maxlength):
> ''' function validated for maximum number of characters '''
> maxlength = int(maxlength)
> if len(value) > maxlength:
> value = value[:maxlength]
> return (value == ' ')
> return True
>
>
> def run():
> root = Tk()
> root.title('test')
> View(root)
> root.mainloop()
>
> if __name__ == "__main__":
> run()
>
> The code works well :-) but...
>
> in vcmd i use this:
>
> vcmd = (self.parent.register(self.maxlength_validate), '%P', 20)
> # '20' argument is my question, is not default value (is max length of
> char, different for each entry... very comfortable for me)
>
> is it all right, according to you, to pass a non-default argument? (no
> error from the interpreter)
>
> Without this way I would not know how to pass the maximum number of
> characters to the validation function, I can not use one variable
> self.--- for each entry ... it would become aesthetically unattractive.
>
> I would not even like to add a textvariable variable because anyway then
>
> I should always pass the comparison value.
>
> thank you in advance
A viable alternative may be to use functools.partial() to pass the
maxlength:
from Tkinter import *
from functools import partial
class View():
def __init__(self, parent):
self.parent = parent
self.make_ui()
def make_ui(self):
''' create user interface '''
def vcmd(maxlength):
return self.parent.register(
partial(self.maxlength_validate, maxlength=maxlength)
), "%P"
self.id_entry = Entry(self.parent, width=6)
# take out the properties for understanding
self.id_entry.configure(validate="key", validatecommand=vcmd(4))
self.id_entry.pack()
self.name_entry = Entry(self.parent, width=30)
# take out the properties for understanding
self.name_entry.configure(validate="key", validatecommand=vcmd(20))
self.name_entry.pack()
def maxlength_validate(self, value, maxlength):
return len(value) <= maxlength
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