QtreeWidgetItem size

Iam using QTreeWidgetItem->headerItem()-> and I want to expand the size of this widget according to size of text of this?

I reliazed that there is no expanding column in treeWidgetItem but in TreeWidget.
I resized column with treeWidget->setCloumnWidth(int column) .Although the size of column is 100 it doesnt show a 100 length.Why?

I want to expand the column as the longest string length but now I am using 5xlength.

Take a look at QHeaderView::setResizeMode and its ResizeToContents option.