python assign list to tk stringvar

Question

I'm having some trouble with stringVars from TK.

from tkinter import *

root = Tk()
strVar = StringVar()
tmp1 = ['one','two','three']
print(tmp1)
print(len(tmp1))

strVar.set(tmp1)
tmp2=strVar.get()
print(tmp2)
print(len(tmp2))

Output is:

['one', 'two', 'three'] 
3
('one', 'two', 'three')
23

As you can see, the format is different. Obviously, the list of strings is internally converted into one string with quotes. What ist the reason and how can I avoid it? For my script I would like to have a list of strings for further processing.

While the idea to assign a list to a string var is funny, that's actually not a bad question, What is going on there? Why is the list first converted to tuple and then to string? E.g. if you pass a number or a dict to the string var, those are converted to str only. — tobias_k
– tobias_k, Commented Oct 1, 2018 at 15:51
Why do you feel like you need to keep your list of strings in a StringVar? What's wrong with using just a normal python list? — Bryan Oakley
– Bryan Oakley, Commented Oct 1, 2018 at 17:33
A better idea might be to just have the user enter a number of strings separated by some special character (space, comma, semicolon, whatever), and then str.split the value of strVar.get() accordingly. That's even easier to use than having to enter all those [, ', etc. — tobias_k
– tobias_k, Commented Oct 1, 2018 at 17:52
Hi, thanks for your replies, I have to admit that I am pretty new to python and especially to TK. Background is that I get a list of strings from a system command like result = subprocess.run(['...']).stdout.decode('ascii') which I pass to a listbox via StringVar. At a later point I want to get the data back from this StringVar to use it further. — Jensenmann
– Jensenmann, Commented Oct 2, 2018 at 6:10
@Jensenmann: you don't need to use a StringVar to move data in and out of a listbox. — Bryan Oakley
– Bryan Oakley, Commented Oct 2, 2018 at 12:39

Jensenmann · Accepted Answer · 2019-10-02 11:51:54Z

1

@tjt263, it's very long time ago, but I think I solved it like

    fdupesSV.set(fdupesList)
    tmp = subprocess.run(['fdupes', '-r',directory.get()], stdout=subprocess.PIPE)

    #first convert bytes to ascii, then split at '\n', then assign so fdupesOut
    fdupesList=tmp.stdout.decode('ascii').split('\n')
    fdupesSV.set(fdupesList)

I am not sure if I remember the issue correctly but I hope it helps you

Cheers Jens

answered Oct 2, 2019 at 11:51

Jensenmann

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figbeam · Accepted Answer · 2018-10-01 20:06:56Z

0

from tkinter import *
import ast

root = Tk()
strVar = StringVar()
tmp1 = ['one','two','three']
print(type(tmp1), tmp1, len(tmp1))

strVar.set(tmp1)
x = ast.literal_eval('[' + strVar.get()[1:-1] + ']')
print(type(x), x, len(x))

answered Oct 1, 2018 at 20:06

figbeam

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3 Comments

Jensenmann Over a year ago

Hi thanks for the post. Even if this works, it seems to me not very clean. Background is that I get a list of strings from a system command like result = subprocess.run(['...']).stdout.decode('ascii') which I pass to a listbox via StringVar. I learned now that StringVar is not designed to hold any lists, so I think I should rather keep the list in a separate python list variable and just convert the list to string before setting the stringvar for the listbox.

voices Over a year ago

@Jensenmann, Hi, that's exactly what I'm trying to do. Did you find a good solution?

Jensenmann Over a year ago

@tjt263, please find my answer above

DonH · Accepted Answer · 2023-10-21 18:59:17Z

0

I've just tested an easy way to do this, which was suggested by tobias_k's comment above

Start with your list of strings, but rather than encoding them, just join the list of strings into a single string using newline or another separator (if your strings might include newline).

Then just split the strings after getting the value.

For example:

# To set the string variable:

list_of_strings = ['Str 1', 'Str 2', 'Str 3']  # your data

list_var = tk.StringVar()
list_var.set('\n'.join(list_of_strings)

# To read the string variable:
received_list = list_var.get().split('\n')

if your initial list of strings includes newlines, then you could use any other character to join the strings.

answered Oct 21, 2023 at 18:59

DonH

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