12. Tree and List Widgets¶
Gtk.TreeView and its associated widgets are an extremely powerful way
of displaying data. They are used in conjunction with a
Gtk.TreeStore and provide a way of displaying and manipulating data
in many ways, including:
- Automatic updates when data is added, removed or edited
- Drag and drop support
- Sorting data
- Embedding widgets such as check boxes, progress bars, etc.
- Reorderable and resizable columns
- Filtering data
With the power and flexibility of a
Gtk.TreeView comes complexity. It
is often difficult for beginner developers to be able to utilize it correctly due
to the number of methods which are required.
12.1. The Model¶
Gtk.TreeView has an associated
contains the data displayed by the TreeView. Each
Gtk.TreeModel can be
used by more than one
Gtk.TreeView. For instance, this allows the same
underlying data to be displayed and edited in 2 different ways at the same time.
Or the 2 Views might display different columns from the same Model data, in the
same way that 2 SQL queries (or “views”) might show different fields from the
same database table.
Although you can theoretically implement your own Model, you will normally use
Gtk.TreeStore model classes.
Gtk.ListStore contains simple rows of data, and each row has no children,
Gtk.TreeStore contains rows of data, and each row may have child
When constructing a model you have to specify the data types for each column the model holds.
store = Gtk.ListStore(str, str, float)
This creates a list store with three columns, two string columns, and a float column.
treeiter = store.append(["The Art of Computer Programming", "Donald E. Knuth", 25.46])
Once data has been inserted, you can retrieve or modify data using the tree iter and column index.
print(store[treeiter]) # Prints value of third column store[treeiter] = 42.15
As with Python’s built-in
list object you can use
len() to get the number
of rows and use slices to retrieve or set values.
# Print number of rows print(len(store)) # Print all but first column print(store[treeiter][1:]) # Print last column print(store[treeiter][-1]) # Set last two columns store[treeiter][1:] = ["Donald Ervin Knuth", 41.99]
Iterating over all rows of a tree model is very simple as well.
for row in store: # Print values of all columns print(row[:])
Keep in mind, that if you use
Gtk.TreeStore, the above code will only
iterate over the rows of the top level, but not the children of the nodes.
To iterate over all rows and its children, use the
def print_tree_store(store): rootiter = store.get_iter_first() print_rows(store, rootiter, "") def print_rows(store, treeiter, indent): while treeiter is not None: print(indent + str(store[treeiter][:])) if store.iter_has_child(treeiter): childiter = store.iter_children(treeiter) print_rows(store, childiter, indent + "\t") treeiter = store.iter_next(treeiter)
Apart from accessing values stored in a
Gtk.TreeModel with the list-like
method mentioned above, it is also possible to
Gtk.TreePath instances. Both reference
a particular row in a tree model.
One can convert a path to an iterator by calling
Gtk.ListStore contains only one level,
i.e. nodes do not have any child nodes, a path is essentially the index of the row
you want to access.
# Get path pointing to 6th row in list store path = Gtk.TreePath(5) treeiter = liststore.get_iter(path) # Get value at 2nd column value = liststore.get_value(treeiter, 1)
In the case of
Gtk.TreeStore, a path is a list of indexes or a string.
The string form is a list of numbers separated by a colon. Each number refers to
the offset at that level. Thus, the path “0” refers to the root node and the
path “2:4” refers to the fifth child of the third node.
# Get path pointing to 5th child of 3rd row in tree store path = Gtk.TreePath([2, 4]) treeiter = treestore.get_iter(path) # Get value at 2nd column value = treestore.get_value(treeiter, 1)
Gtk.TreePath can be accessed like lists, i.e.
len(treepath) returns the depth of the item
treepath is pointing to,
treepath[i] returns the child’s index on the i-th level.
12.2. The View¶
While there are several different models to choose from, there is only one view
widget to deal with. It works with either the list or the tree store. Setting up
Gtk.TreeView is not a difficult matter. It needs a
Gtk.TreeModel to know where to retrieve its data from, either by
passing it to the
Gtk.TreeView constructor, or by calling
tree = Gtk.TreeView(store)
Gtk.TreeView widget has a model, it will need to know how to
display the model. It does this with columns and cell renderers.
Cell renderers are used to draw the data in the tree model in a way. There are a
number of cell renderers that come with GTK+, for instance
In addition, it is relatively easy to write a custom renderer yourself.
Gtk.TreeViewColumn is the object that
Gtk.TreeView uses to
organize the vertical columns in the tree view. It needs to know the name of the
column to label for the user, what type of cell renderer to use, and which piece
of data to retrieve from the model for a given row.
renderer = Gtk.CellRendererText() column = Gtk.TreeViewColumn("Title", renderer, text=0) tree.append_column(column)
column = Gtk.TreeViewColumn("Title and Author") title = Gtk.CellRendererText() author = Gtk.CellRendererText() column.pack_start(title, True) column.pack_start(author, True) column.add_attribute(title, "text", 0) column.add_attribute(author, "text", 1) tree.append_column(column)
12.3. The Selection¶
Most applications will need to not only deal with displaying data, but also receiving input events from users. To do this, simply get a reference to a selection object and connect to the “changed” signal.
select = tree.get_selection() select.connect("changed", on_tree_selection_changed)
Then to retrieve data for the row selected:
def on_tree_selection_changed(selection): model, treeiter = selection.get_selected() if treeiter is not None: print("You selected", model[treeiter])
You can control what selections are allowed by calling
Gtk.TreeSelection.get_selected() does not work if the selection mode is
12.4.1. Sorting by clicking on columns¶
model = Gtk.ListStore(str) model.append(["Benjamin"]) model.append(["Charles"]) model.append(["alfred"]) model.append(["Alfred"]) model.append(["David"]) model.append(["charles"]) model.append(["david"]) model.append(["benjamin"]) treeView = Gtk.TreeView(model) cellRenderer = Gtk.CellRendererText() column = Gtk.TreeViewColumn("Title", renderer, text=0)
The next step is to enable sorting. Note that the column_id (
0 in the example) refers to the column of the model and not to the TreeView’s column.
12.4.2. Setting a custom sort function¶
It is also possible to set a custom comparison function in order to change the sorting behaviour. As an example we will create a comparison function that sorts case-sensitive. In the example above the sorted list looked like:
alfred Alfred benjamin Benjamin charles Charles david David
The case-sensitive sorted list will look like:
Alfred Benjamin Charles David alfred benjamin charles david
First of all a comparison function is needed. This function gets two rows and has to return a negative integer if the first one should come before the second one, zero if they are equal and a positive integer if the second one should come before the second one.
def compare(model, row1, row2, user_data): sort_column, _ = model.get_sort_column_id() value1 = model.get_value(row1, sort_column) value2 = model.get_value(row2, sort_column) if value1 < value2: return -1 elif value1 == value2: return 0 else: return 1
Then the sort function has to be set by
model.set_sort_func(0, compare, None)
Unlike sorting, filtering is not handled by the two models we previously saw, but by the
Gtk.TreeModelFilter class. This class, like
Gtk.ListStore, is a
Gtk.TreeModel. It acts as a layer between the “real” model (a
Gtk.TreeStore or a
Gtk.ListStore), hiding some elements to the view. In practice, it supplies the
Gtk.TreeView with a subset of the underlying model. Instances of
Gtk.TreeModelFilter can be stacked one onto another, to use multiple filters on the same model (in the same way you’d use “AND” clauses in a SQL request). They can also be chained with
filter = model.filter_new()
In the same way the sorting function works, the
Gtk.TreeModelFilter needs a “visibility” function, which, given a row from the underlying model, will return a boolean indicating if this row should be filtered out or not. It’s set by
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import gi gi.require_version('Gtk', '3.0') from gi.repository import Gtk #list of tuples for each software, containing the software name, initial release, and main programming languages used software_list = [("Firefox", 2002, "C++"), ("Eclipse", 2004, "Java" ), ("Pitivi", 2004, "Python"), ("Netbeans", 1996, "Java"), ("Chrome", 2008, "C++"), ("Filezilla", 2001, "C++"), ("Bazaar", 2005, "Python"), ("Git", 2005, "C"), ("Linux Kernel", 1991, "C"), ("GCC", 1987, "C"), ("Frostwire", 2004, "Java")] class TreeViewFilterWindow(Gtk.Window): def __init__(self): Gtk.Window.__init__(self, title="Treeview Filter Demo") self.set_border_width(10) #Setting up the self.grid in which the elements are to be positionned self.grid = Gtk.Grid() self.grid.set_column_homogeneous(True) self.grid.set_row_homogeneous(True) self.add(self.grid) #Creating the ListStore model self.software_liststore = Gtk.ListStore(str, int, str) for software_ref in software_list: self.software_liststore.append(list(software_ref)) self.current_filter_language = None #Creating the filter, feeding it with the liststore model self.language_filter = self.software_liststore.filter_new() #setting the filter function, note that we're not using the self.language_filter.set_visible_func(self.language_filter_func) #creating the treeview, making it use the filter as a model, and adding the columns self.treeview = Gtk.TreeView.new_with_model(self.language_filter) for i, column_title in enumerate(["Software", "Release Year", "Programming Language"]): renderer = Gtk.CellRendererText() column = Gtk.TreeViewColumn(column_title, renderer, text=i) self.treeview.append_column(column) #creating buttons to filter by programming language, and setting up their events self.buttons = list() for prog_language in ["Java", "C", "C++", "Python", "None"]: button = Gtk.Button(prog_language) self.buttons.append(button) button.connect("clicked", self.on_selection_button_clicked) #setting up the layout, putting the treeview in a scrollwindow, and the buttons in a row self.scrollable_treelist = Gtk.ScrolledWindow() self.scrollable_treelist.set_vexpand(True) self.grid.attach(self.scrollable_treelist, 0, 0, 8, 10) self.grid.attach_next_to(self.buttons, self.scrollable_treelist, Gtk.PositionType.BOTTOM, 1, 1) for i, button in enumerate(self.buttons[1:]): self.grid.attach_next_to(button, self.buttons[i], Gtk.PositionType.RIGHT, 1, 1) self.scrollable_treelist.add(self.treeview) self.show_all() def language_filter_func(self, model, iter, data): """Tests if the language in the row is the one in the filter""" if self.current_filter_language is None or self.current_filter_language == "None": return True else: return model[iter] == self.current_filter_language def on_selection_button_clicked(self, widget): """Called on any of the button clicks""" #we set the current language filter to the button's label self.current_filter_language = widget.get_label() print("%s language selected!" % self.current_filter_language) #we update the filter, which updates in turn the view self.language_filter.refilter() win = TreeViewFilterWindow() win.connect("destroy", Gtk.main_quit) win.show_all() Gtk.main()