How to set flag for an item in a QTreeWidget?

Question

I have a QTreeWidget which contains two columns and some rows. I would like to set a flag so that if an item in the second column is either a zero or empty, it cannot be edited. If the item clicked is not numeric, it will be shown with a red text.

My code:

def qtree_check_item(self, item, column):
    item.setFlags(QtCore.Qt.ItemIsEnabled)
    if column == 1:
        if item.text(1) != '0':
            item.setFlags(item.flags() | QtCore.Qt.ItemIsEditable)
        if not item.text(1).isnumeric():
            item.setForeground(1, QtGui.QBrush(QtGui.QColor("red")))

This works if the item is zero. If I replace:

if item.text(1) != '0':

with

if item.text(1) != '':

This works for empty strings. But if I combine both using:

if item.text(1) != '0' or item.text(1) != '':

The flags are not set. What am I doing wrong?

@G.M. - That works...do you know why and is required in this case as I assumed or would have been more logical? Also please post your comment as an answer :) — Joseph

G.M. G.M. · Accepted Answer · 2018-01-18T11:30:09

I would like to set a flag so that if an item in the second column is either a zero or empty, it cannot be edited.

You then have...

if item.text(1) != '0' or item.text(1) != '':
    item.setFlags(item.flags() | QtCore.Qt.ItemIsEditable)

Now consider what happens if item.text(1) == '0'. In that case the second test item.text(1) != '' passes and the conditional as a whole passes due to the or. Likewise if item.text(1) == '' is true then the test item.text(1) != '0' will pass and the entire conditional pass as a result.

So, you only want to set the editable flag if both...

item.text(1) != '0' and item.text(1) != ''

hold true.

To put it another way, since item.text(1) cannot be equal to both '0' and '' at the same time the conditional...

if item.text(1) != '0' or item.text(1) != '':

is essentially...

if True or False:

which will always pass.

(Sorry if that all seems a bit convoluted.)

How to set flag for an item in a QTreeWidget?

1 Answers