Why does clicking on any menu item always start the last one?

Question

In Python, I am trying to generate a menu using a for loop, but when I click on any menu item, the last menu item is always triggered, how can I fix this? I am using Tkinter.

font_sizes = [
    str ('8' ),
    str ('9' ),
    str ("10"),
    str ("11"),
    str ("12"),
    str ("14"),
    str ("16"),
    str ("18"),
    str ("20"),
    str ("22"),
    str ("24"),
    str ("26"),
    str ("28"),
    str ("36"),
    str ("48"),
    str ("72"),
];

for font_size in font_sizes :
    font_size_menu.add_command (
        label = font_size,
        command = lambda : function (font_size),
    );

See https://stackoverflow.com/questions/10865116/ – Bryan Oakley Oct 09 '22 at 18:06 — Bryan Oakley, Oct 09 '22 at 18:06

score 1 · Accepted Answer · answered Oct 09 '22 at 18:07

This is a tricky corner of Python. The issue is that the lambda captures the name font_size, not the value. So, by the time any of those functions run, the value of font_size is "72". You work around this by "capturing" the value as a default parameter. As a side note, you don't ever need to call str on a string. And we do not use semi-colons as statement terminators in Python.

font_sizes = [
    '8','9','10','11','12','14','16','18',
    '20','22','24','26','28','30','48','72'
]

for font_size in font_sizes :
    font_size_menu.add_command (
        label = font_size,
        command = lambda font_size=font_size: function (font_size),
    )

Why does clicking on any menu item always start the last one?

1 Answers1