当用户继续在TKinter中更改值（使用跟踪方法）时，使用Entry并更新输入的条目

Question

I am learning Python and I am starting to learn how to use the TKinter GUI. I am making a small interface that does some simple statistical analysis like STDEV, T-tests, etc. I have this method in a class which basically gets the data to work with.

I want the user to be able enter as many data entries as they want (I mean as long as the computer can handle of course). The problem I am having is -- I think when I use the method .get() on an Entry, None is returned?

I am also using method .trace() of DoubleVar() to trace when the values of the entries are updated using the method shown here:

Python Tkinter update when entry is changed

I thought it made sense but it's not working for me. Whenever I change a box in my TK interface, all the other boxes get changed, but the values used to calculate standard deviation are not the numbers that are being shown on the Entry boxes (which are all the same anyways).

Here is the code:

class StandardDeviation: """ Runs standard deivation calculations. """

def __init__(self) -> None:
    """
    Initializes an instance of the functions!
    """
    self.stdev_pop = Button(top_frame,
                            text="Calculate the population "
                                 "standard deviation of the data set")
    self.stdev_pop.bind("<Button-1>", self.show_result_population)
    self.stdev_pop.pack()
    stdev_samp = Button(top_frame,
                        text="Calculate the sample "
                             "standard deviation of the data set")
    stdev_samp.bind("<Button-1>", self.show_result_sample)
    stdev_samp.pack()
    self.data = []
    self.enter_data = Button(top_frame, text="Enter data")
    self.enter_data.bind("<Button-1>", self.pack_add_entry_button)

    self.add_entry = Button(top_frame, text="Add data entry",
                            command=self.add_new_entry)
    self.enter_data.pack()
    self.all_entries = {}
    self.tracer = DoubleVar()
    self.tracer.trace("w", self.update)

def pack_add_entry_button(self, *args) -> None:
    """
    Pack the add_entry button.
    """
    self.add_entry.pack()

def update(self, *args) -> None:
    """
    Update the values of the entries.
    """
    global update_in_progress
    if update_in_progress:
        return
    update_in_progress = True
    data = [str(self.all_entries[item]) for item in self.all_entries]
    self.data = [int(item) for item in data if item.isnumeric()]
    update_in_progress = False

def add_new_entry(self):
    """
    Add a new entry.
    """
    new_entry = Entry(root, textvariable=self.tracer)
    new_entry.pack()
    new_entry_data = new_entry.get()
    self.all_entries[new_entry] = new_entry_data 

I'm not sure where I'm wrong here if anyone could help me I'd really appreciate it. Thank you!

Answer 1

There is no way to run the code you posted as the indentation is off and some of the buttons call functions that don't exist so this is a standard trace program that shows how to use the tkinter variable associated with the trace, a StringVar in ths case, to get the contents.

import tkinter

def text_changed(*args):
    print(tk_name.get())

top = tkinter.Tk()

tk_name=tkinter.StringVar()
tk_name.set("nothing")
tk_name.trace("w", text_changed)

tkinter.Label(top, textvariable=tk_name).grid(row=0, column=1)

entry_1 = tkinter.Entry(top, textvariable=tk_name)
entry_1.grid(row=1, column=1, sticky="W")
entry_1.focus_set()

top.mainloop()