Why am I getting the error 'NoneType' object has no attribute 'set' in python 3.6.7?

Question

I am cleaning up some code, I originally had:

program_lbl = Label(input_frame, text="Program")
program_lbl.grid(column=1, row=0)
program_combo = Combobox(input_frame, values = ['program1', 'program2'], state = "readonly", width = 8)
program_combo.grid(column=1, row=1)
program_combo.set('program1') #set program1 as default

and I condensed it to:

program_lbl = Label(input_frame, text="Program").grid(column=1, row=0)
program_combo = Combobox(input_frame, values = ['program1', 'program2'], state = "readonly", width = 8).grid(column=1, row=1)
program_combo.set('HUNTER') #set program1 as default

but I get the following error:

Traceback (most recent call last):
  File "c:\Users\j56967\.vscode\extensions\ms-python.python-2019.3.6558\pythonFiles\ptvsd_launcher.py", line 45, in <module>
    main(ptvsdArgs)
  File "c:\Users\j56967\.vscode\extensions\ms-python.python-2019.3.6558\pythonFiles\lib\python\ptvsd\__main__.py", line 391, in main
    run()
  File "c:\Users\j56967\.vscode\extensions\ms-python.python-2019.3.6558\pythonFiles\lib\python\ptvsd\__main__.py", line 272, in run_file
    runpy.run_path(target, run_name='__main__')
  File "C:\Python367-64\lib\runpy.py", line 263, in run_path
    pkg_name=pkg_name, script_name=fname)
  File "C:\Python367-64\lib\runpy.py", line 96, in _run_module_code
    mod_name, mod_spec, pkg_name, script_name)
  File "C:\Python367-64\lib\runpy.py", line 85, in _run_code
    exec(code, run_globals)
  File "c:\Users\j56967\Documents\python\gui_refinement.py", line 46, in <module>
    program_combo.set('program1')
AttributeError: 'NoneType' object has no attribute 'set'

When I comment out the program_combo.set('program1') line everything works but the combobox has no default selection.

EDIT: The duplicate marked below has a great answer to my question, thank you.

`grid(column=1, row=1)` works inplace, returns `None`. – Quang Hoang Aug 02 '19 at 16:47 — Quang Hoang, Aug 02 '19 at 16:47

score 0 · Answer 1 · answered Aug 02 '19 at 16:48

program_lbl = Label(input_frame, text="Program")
program_lbl.grid(column=1, row=0)

Here, you're creating a Label and then calling grid() on it.

program_lbl = Label(input_frame, text="Program").grid(column=1, row=0)

Here, you're creating an object from Label(...).grid(...), which returns nothing.

Why am I getting the error 'NoneType' object has no attribute 'set' in python 3.6.7?

1 Answers1