Tkinter error for a scheduled event

[Ceegen]

Scheduled a variable to be updated with the current time for display in a label.

...

def update_clock():
    tab1_labeltxt = StringVar(time.strftime('%H %M %S'))
    brass_io.after(1000, update_clock)

brass_io.after(1000, update_clock)
brass_io.mainloop()

Program works just fine without the above code, which produces this error:

Exception in Tkinter callback

Error:
Traceback (most recent call last):
  File "/usr/lib/python3.6/tkinter/__init__.py", line 1705, in __call__
    return self.func(*args)
  File "/usr/lib/python3.6/tkinter/__init__.py", line 749, in callit
    func(*args)
  File ".../BIBO_Project.py", line 100, in update_clock
    tab1_labeltxt = StringVar(time.strftime('%H %M %S'))
  File "/usr/lib/python3.6/tkinter/__init__.py", line 480, in __init__
    Variable.__init__(self, master, value, name)
  File "/usr/lib/python3.6/tkinter/__init__.py", line 317, in __init__
    self._root = master._root()
AttributeError: 'str' object has no attribute '_root'

Not sure what to do. Above my pay-grade.

Did some testing though, and I can't find this exact problem elsewhere, but I did see something about it being a possible problem with class inheritance? I really don't know, very new to this.

Thanks in advance <3

[edit] currently reading this: http://effbot.org/tkinterbook/variable.htm which seems to be getting somewhere.
[edit 2] nope lol. still looking.