框架对象没有属性

Question

Part of a GUI program I'm building needs to be able to convert times given into seconds. The frame class in my GUI that does this is giving me some trouble. I created an instance variable of type combobox to hold the options for types of time period to convert. I bound the combobox selection to convert the input time into seconds. I want to tie entering values into the entry box to doing the same thing. I tried to call my conversion function in my validation command function for the entry box, but it's telling me that my frame object "PERIODIC" doesn't have an attribute "period_type". I'm confused because I named the combobox as an instance variable, and it should be accessible to everything in the class. "self.period_type" is right there in my init. Why can't I access this variable? Am I missing something painfully obvious?

The Traceback I'm getting is:

Exception in Tkinter callback
Traceback (most recent call last):
  File "C:\Users\4D_User\AppData\Local\Programs\Python\Python38-32\lib\tkinter\__init__.py", line 1883, in __call__
    return self.func(*args)
  File "C:/Users/PycharmProjects/LoggerProject/Scripts/ProblemExample.py", line 37, in ValidateTime
    self.convert_time(self.period_type.get())
AttributeError: 'PERIODIC' object has no attribute 'period_type'<

This is my code:

from tkinter import ttk
import re

root = tk.Tk()

class PERIODIC(tk.Frame):
    def __init__(self, container, **kwargs):
        super().__init__(container, **kwargs)
        self.time_unconverted = tk.DoubleVar()
        self.time_converted = tk.DoubleVar()
        self.periodic_label = tk.Label(self, text="PERIODIC")
        self.periodic_label.grid(row=0, columnspan=2, sticky="NSEW")
        trigger_option_label = ttk.Label(self, text="Trigger Every: ")
        trigger_option_label.grid(row=1, column=0)
        vcmd = (self.register(self.ValidateTime), '%P')
        self.num_period = tk.Entry(self,textvariable=self.time_unconverted, validate="key", validatecommand=vcmd)
        self.num_period.grid(row=1, column=1)
        self.period_type = ttk.Combobox(self, values=["seconds", "minutes", "hours", "days"])
        self.period_type.bind("<<ComboboxSelected>>", lambda y: self.convert_time(self.period_type.get()))
        self.period_type.grid(row=1, column=2)

    def convert_time(self, type):
        if type == 'seconds':
            self.time_converted.set(self.time_unconverted.get())
        if type == 'minutes':
            self.time_converted.set(self.time_unconverted.get() * 60)
        if type == 'hours':
            self.time_converted.set(self.time_unconverted.get() * 3600)
        if type == 'days':
            self.time_converted.set(self.time_unconverted.get() * 86400)


    def ValidateTime(self, P):
        test = re.compile('^[0-9]{1,3}?\.?[0-9]?$')
        if test.match(P):
            self.convert_time(self.period_type.get())
            return True
        else:
            return False

frame = PERIODIC(root)
frame.grid(row=0,column=0)
root.mainloop()

Answer 1

Your validation command is being triggered when you create the entry, and it's using self.period_type which hasn't been defined yet.

The simple solution is to move the creation of the combobox prior to creating the entry.