You can use subprocess.check_output() to get output and assign to Label

You can also import script and execute function from script.

import testtest.function()

But first you will have to redirect sys.stdout using class with write() and then it will catch all printed text.

You can redirect sys.stdout to variable (see StdoutRedirector) and then you can edit it (ie. strip \n at the end) or you can redirect directly to Label (see StdoutRedirectorLabel)

import Tkinter as tk# -----import subprocessdef callback1():    cmd = 'python test.py'    # it will execute script which runs only `function1`    output = subprocess.check_output(cmd, shell=True)    lbl['text'] = output.strip()# -----class StdoutRedirector(object):    def __init__(self):        # clear before get all values        self.result = ''    def write(self, text):        # have to use += because one `print()` executes `sys.stdout` many times        self.result += textdef callback2():    import test    # keep original `sys.stdout    old_stdout = sys.stdout    # redirect to class which has `self.result`    sys.stdout = StdoutRedirector()    # it will execute only `function2`    test.function2()    # assign result to label (after removing ending "\n")    lbl['text'] = sys.stdout.result.strip()    # set back original `sys.stdout    sys.stdout = old_stdout# -----import sysclass StdoutRedirectorLabel(object):    def __init__(self, widget):        self.widget = widget        # clear at start because it will use +=        self.widget['text'] = ''    def write(self, text):        # have to use += because one `print()` executes `sys.stdout` many times        self.widget['text'] += textdef callback3():    import test    # keep original `sys.stdout    old_stdout = sys.stdout    # redirect to class which will add text to `lbl`    sys.stdout = StdoutRedirectorLabel(lbl)    # it will execute only `function3` and assign result to Label (with ending "\n")    test.function3()    # set back original `sys.stdout    sys.stdout = old_stdout# --- main ---master = tk.Tk()master.geometry('200x200')lbl = tk.Label(master, text='')lbl.pack()btn1 = tk.Button(master, text="subprocess", command=callback1)btn1.pack()btn2 = tk.Button(master, text="StdoutRedirector", command=callback2)btn2.pack()btn3 = tk.Button(master, text="StdoutRedirectorLabel", command=callback3)btn3.pack()master.mainloop()

test.py

def function1():    print('function 1')def function2():    print('function 2')def function3():    print('function 3')if __name__ == '__main__':    function1() 

In a method when a line with return ... is run, nothing else will be seen that comes after that line, as in your 2nd line of return ... is effectively useless as return cooz() is run unconditionally. You could simply replace your main with:

def main():    return cooz(), tooz()

and accordingly your printSomething:

x, y = helloworld.main()

Returning all methods/functions from a script without explicitly passing method names:

Well, I stand corrected, based on this answer you can do it fairly simply. For calling all methods or functions this answer helped a lot.

Let's say there's a script named hello_world.py:

def hello_world():    print("Hello World!")    print("this is the 2nd line of this method")def multiplication(*args):    mult = 1    for arg in args:        mult *= arg    return multdef some_other_method():    print("some other method")    print(multiplication(2, 3, 5, 7))

is in the same directory as GUI script below:

import tkinter as tk    # required for the GUIimport subprocess       # required for redirecting stdout to GUIimport sys, inspect     # required for all methods and functions redirectionimport hello_world      # the script file that is redirecteddef redirect(module, method):    '''Redirects stdout from the method or function in module as a string.'''    proc = subprocess.Popen(["python", "-c",        "import " + module.__name__ + ";" + module.__name__ + "." + method + "()"],                                                                stdout=subprocess.PIPE)    out = proc.communicate()[0]    return out.decode('unicode_escape')def redirect_module(module):    '''Retruns all stdout from all methods or functions in module as a string.'''    # to filter out non-method, and non-function attributes    all_mtds_or_funcs = inspect.getmembers(sys.modules[module.__name__],                                                 inspect.isfunction or inspect.ismethod)    red_str_buffer = ""    for method in all_mtds_or_funcs:        red_str_buffer += redirect(module, method[0]) + "\n---\n"    return red_str_bufferdef put_in_txt(module):    '''Puts the redirected string in a text.'''    txt.insert('1.0', redirect_module(module))root = tk.Tk()txt = tk.Text(root)btn = tk.Button(root, text="Redirect")btn['command'] = lambda module=hello_world : put_in_txt(module)txt.pack()btn.pack()root.mainloop()

which returns console output of all methods and functions in hello_world.py as a string. Based on this suggestion it then puts that string in a Text field.