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.
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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
Steve
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