Category: Python

How to get preset paths in Blender Python

2020-10-01 Blender Python Tips

This is a tips for blender addon developers.

GOAL

To get the list of paths to preset directories, blender system preset and user preset and so on.

These are examples of the preset directory.

presets of interface theme
- C:\Program Files\Blender Foundation\Blender 2.83\2.83\scripts\presets\interface_theme
- C:\Program Files\Blender Foundation\Blender 2.83\2.83\scripts\addons\presets\interface_theme’
presets of keyconfig
- C:\Program Files\Blender Foundation\Blender 2.83\2.83\scripts\presets\keyconfig
- C:\Users\<USER_NAME>\AppData\Roaming\Blender Foundation\Blender\2.83\scripts\presets\keyconfig

Environment

Blender 2.83 (Python 3.7.4)
Windows 10

Method

Use bpy.utils.preset_paths(subdir) that returns the list of paths to the preset directory of subdir.

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How to remove widget from the layout in PySide

2020-09-29 Python

I’d like to add close button to the single widget and remove the widget from the parent layout when the close button pressed.

GOAL

To remove single widget with close button as below.

Environment

Windows 10
Python 3.8.7
PySide2 5.15.2

Method

1. Create a widget with close button and set it in the layout

I create ItemWidget with close button and put the item and add button on the main window. Check “How To Insert Widget To The Layout Counting From The End” for detail about the implement of add button.

import sys
from PySide2.QtWidgets import *

class ItemWidget(QWidget):
    def __init__(self, id_str="", parent=None):
        super(ItemWidget, self).__init__(parent)
        self.id_str = id_str
        self._generateUI()
    def _generateUI(self):
        main_layout = QGridLayout()
        self.setLayout(main_layout)
        title = QLabel("title" + self.id_str)
        main_layout.addWidget(title, 0, 0, 1, 3)
        close_button = QPushButton("-")
        close_button.setFixedWidth(30)
        main_layout.addWidget(close_button, 0, 3, 1, 1)
        spinbox = QSpinBox()
        main_layout.addWidget(spinbox, 1, 0, 1, 4)

class MyMainWindow(QMainWindow):
    def __init__(self, parent=None):
        super(MyMainWindow, self).__init__(parent)
        self.id_num = 1
        self._generateUI()
    def _generateUI(self):
        main_widget = QWidget()
        self.main_layout = QVBoxLayout()
        main_widget.setLayout(self.main_layout)
        self.setCentralWidget(main_widget)
        item = ItemWidget(str(self.id_num))
        self.main_layout.addWidget(item)
        add_button = QPushButton("+")
        add_button.clicked.connect(self._addItem)
        self.main_layout.addWidget(add_button)
    def _addItem(self):
        self.id_num += 1
        item = ItemWidget(str(self.id_num))
        self.main_layout.insertWidget(self.main_layout.count()-1, item)

def launch():
    app = QApplication.instance()
    if not app:
        app = QApplication(sys.argv)
    widget = MyMainWindow()
    widget.show()
    app.exec_()

launch()

2. Connect close function to the signal “clicked” of the close button

Use deleteLater() to delete widget.

class ItemWidget(QWidget):
    def __init__(self, id_str="", parent=None):
        super(ItemWidget, self).__init__(parent)
        self.id_str = id_str
        self._generateUI()
    def _generateUI(self):
        main_layout = QGridLayout()
        self.setLayout(main_layout)
        title = QLabel("title" + self.id_str)
        main_layout.addWidget(title, 0, 0, 1, 3)
        close_button = QPushButton("-")
        close_button.setFixedWidth(30)
        close_button.clicked.connect(self._close_widget) # add to close the widget
        main_layout.addWidget(close_button, 0, 3, 1, 1)
        spinbox = QSpinBox()
        main_layout.addWidget(spinbox, 1, 0, 1, 4)
    def _close_widget(self):
        self.deleteLater() # main function to close widget

* There are many ways to remove widget from the parent layout. For example, some people use setParent(None) or something. However don’t use removeWidget() because it just removes widget without destroying it. Please refer to the discussion below.

Is deleteLater() necessary in PyQt/PySide? in stackoverflow.com
pyqt: how to remove a widget? in stackoverflow.com

3. Resize the parent widget when the child removed

The function deleteLater() just delete the widget without changing the size. So I changed size manually with adjustSize() as below.
Related article: How to detect the child widget destroy?

class MyMainWindow(QMainWindow):
    def __init__(self, parent=None):
        super(MyMainWindow, self).__init__(parent)
        self.id_num = 1
        self._generateUI()
    def _generateUI(self):
        main_widget = QWidget()
        self.main_layout = QVBoxLayout()
        main_widget.setLayout(self.main_layout)
        self.setCentralWidget(main_widget)
        item = ItemWidget(str(self.id_num))
        self.main_layout.addWidget(item)
        add_button = QPushButton("+")
        add_button.clicked.connect(self._addItem)
        self.main_layout.addWidget(add_button)
    def _addItem(self):
        self.id_num += 1
        item = ItemWidget(str(self.id_num))
        self.main_layout.insertWidget(self.main_layout.count()-1, item)
    def _deletedItem(self, item):
        self.id_num -= 1
        for i in range(3):
            QApplication.processEvents()
        self.adjustSize()

I don’t know why but adjustSize() doesn’t work correctly until some events are processed in the event loop. So I called QApplication.processEvents() in the for loop. Please let me know if you have any idea about this

Reference: PySide: What is the best way to resize the main window if one widget is hidden? in stackoverflow.com

How to detect the child widget destroy?

2020-09-27 Python

GOAL

To do some functions when the child widget is deleted.

Environment

Windows 10
Python 3.8.7
PySide2 5.15.2

Method

Connect the function to child’s signal “destroyed” as below.

import sys
from PySide2.QtWidgets import *

class ItemWidget(QWidget):
    def __init__(self, id_str="", parent=None):
        super(ItemWidget, self).__init__(parent)
        self._generateUI()
    def _generateUI(self):
        main_layout = QGridLayout()
        self.setLayout(main_layout)
        title = QLabel("title")
        main_layout.addWidget(title, 0, 0, 1, 3)
        close_button = QPushButton("×")
        close_button.setFixedWidth(30)
        close_button.clicked.connect(self._close_widget)
        main_layout.addWidget(close_button, 0, 3, 1, 1)
    def _close_widget(self):
        self.deleteLater()

class MyMainWindow(QMainWindow):
    def __init__(self, parent=None):
        super(MyMainWindow, self).__init__(parent)
        self._generateUI()
    def _generateUI(self):
        main_widget = QWidget()
        self.main_layout = QVBoxLayout()
        main_widget.setLayout(self.main_layout)
        self.setCentralWidget(main_widget)
        item = ItemWidget(str(self.id_num))
        item.destroyed.connect(self._deletedItemFunc) # connect the function to execute
        self.main_layout.addWidget(item)
    def _deletedItemFunc(self):
        print("deleted") # when the item deleted, the message "deleted" is displayed

def launch():
    app = QApplication.instance()
    if not app:
        app = QApplication(sys.argv)
    widget = MyMainWindow()
    widget.show()
    app.exec_()

launch()

When click × button, the child widget deleted and the message “deleted” is displayed.

Appendix

If the child is removed from the parent layout. You can add function at the same time.

self.main_layout.removeWIdget(item)
self._deletedItemFunc()

How To Insert Widget To The Layout Counting From The End

2020-09-25 Python

GOAL

To insert widget to the layout counting from the end. For example, I’d like to create the add button to add widget at the second position from the end as below.

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How to fit the widget to the parent layout in PySide2

2020-09-23 Python Tips

GOAL

To fit the sizes of the children widgets to the layout of the parent. In other words, to remove the space around widgets from the layout.

Environment

Windows 10
Python 3.8.7
PySide2 5.15.2

Method

There are 2 steps to delete margin space from the layout.

Set the margin of the layout 0
Set the spacing of the layout 0

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How to fit the selected color to the cell in QTreeWidget

2020-09-21 Python Tips

The length of selected color depends on the length of the string in QTreeWidget of PySide2. How can I fit the length of the cell?

GOAL

To fill the color to fit the size of the cell when the item is selected. (See the article “How to select one column of QTreeWidgetItem in PySide2” to generate an tree widget that allows users to select each item.)

Environment

Windows 10
Python 3.8.7
PySide2 5.15.2

Method

Set show-decoration-selected of qss(QStyleSheet) that can be used for QTreeWidget, QTreeView, QListWidget and QListView.

Controls whether selections in a QListView cover the entire row or just the extent of the text.
from Qt Style Sheets Reference

Use setStyleSheet to set qss to the widget as below.

self.tree_widget.setStyleSheet('QTreeView { show-decoration-selected: 1;}')

See the official documentation “Qt Style Sheets” for details about qss.

How to select one column of QTreeWidgetItem in PySide2

2020-09-19 Python

GOAL

To allow users to select one column from the QTreeWidget as below. (If you’d like to know how to generate tree widget, check “How to use QTreeWidget() in PySide2” first.)

Environment

Windows 10
Python 3.8.7
PySide2 5.15.2

Method

Use SelectionBehavior.

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[Tips]How to access each n-th item of lists

2020-09-17 Python Tips

Though the following is one of the ways to access items of multiple list, an error “index out of range” will occur when the lengths of the lists are different. How can I solve it?

list1 = ["A", "B", "C", "D"]
list2 = [1, 2, 3, 4]
list3 = ["Apple", "Orange", "Banana", "Peach"]

for i in range(len(list1)):
    print(list1[i], list2[i], list3[i])

The output is as below.

A 1 Apple
B 2 Orange
C 3 Banana
D 4 Peach

GOAL

To access each n-th item of multiple lists in one for loop.

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How to change the default size of PySide window

2020-09-15 Python

GOAL

To change the default size that is initial size of the window in PySide2.

Environment

Windows 10
Python 3.8.7
PySide2 5.15.2

Method

I create a simple window as below.

import sys
from PySide2.QtWidgets import *

class MyMainWindow(QMainWindow):
    def __init__(self, parent=None):
        super(MyMainWindow, self).__init__(parent)
        self._generateUI()

    def _generateUI(self):
        main_widget = QWidget()
        main_layout = QVBoxLayout()
        main_widget.setLayout(main_layout)
        self.setCentralWidget(main_widget)
        button = QPushButton("Button")
        main_layout.addWidget(button)

def launch():
    app = QApplication.instance()
    if not app:
        app = QApplication(sys.argv)
    widget = MyMainWindow()
    widget.show()
    app.exec_()

launch()

How to change the variable size

Use resize() function at first to change the default size.

from PySide2 import QtCore

class MyMainWindow(QMainWindow):
    def __init__(self, parent=None):
        super(MyMainWindow, self).__init__(parent)
        self._generateUI()
        self.resize(200, 300)

How to change the variable width and height

You can change only width or height of the window using height() or width() to get current size.

def launch():
    app = QApplication.instance()
    if not app:
        app = QApplication(sys.argv)
    widget = MyMainWindow()
    widget.show()
    widget.resize(250, widget.height())

Because the window size is adjusted to the contents of the window, resize after showing the window.

class MyMainWindow(QMainWindow):
    def __init__(self, parent=None):
        super(MyMainWindow, self).__init__(parent)
        self._generateUI()
        print(self.width(), self.height())
        # output => 640 480

def launch():
    app = QApplication.instance()
    if not app:
        app = QApplication(sys.argv)
    widget = MyMainWindow()
    widget.show()
    print(widget.width(), widget.height())
    # output => 200 100

Appendix

How to change the fixed size

Use setFixedSize() to fix the size of window. (You can’t resize the window after using this function.)

class MyMainWindow(QMainWindow):
    def __init__(self, parent=None):
        super(MyMainWindow, self).__init__(parent)
        self.setFixedSize(200, 300)
        self._generateUI()

How to change the fixed height and width.

Use setFixedWidth() and setFixedHeight(). If you use setFixedWidth(), you can still change the height of the window.

class MyMainWindow(QMainWindow):
    def __init__(self, parent=None):
        super(MyMainWindow, self).__init__(parent)
        self.setFixedWidth(250)
        self._generateUI()

How to use QTreeWidget() in PySide2

2020-09-13 Python

GOAL

To create tree widget in my GUI program with PySide2.

Environment

Windows 10
Python 3.8.7
PySide2 5.15.2

Examples

I created sample window and 4 types of tree widgets and 2 functions. The below is the template.

import sys
from PySide2.QtWidgets import *

class MyMainWindow(QMainWindow):
    def __init__(self, parent=None):
        super(MyMainWindow, self).__init__(parent)
        self._generateUI()
        #self._simple_tree_widget()
        self._tree_widget1()
        
    def _generateUI(self):
        main_widget = QWidget()
        main_layout = QVBoxLayout()
        main_widget.setLayout(main_layout)
        self.setCentralWidget(main_widget)
        self.tree_widget = QTreeWidget()
        main_layout.addWidget(self.tree_widget)
    def _tree_widget1(self):
        ...
    def _tree_widget2(self):
        ...

def launch():
    app = QApplication.instance()
    if not app:
        app = QApplication(sys.argv)
    widget = MyMainWindow()
    widget.show()
    app.exec_()

launch()

Example 1. Simple tree widget

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Category: Python

GOAL

Environment

Method

GOAL

Environment

Method

1. Create a widget with close button and set it in the layout

2. Connect close function to the signal “clicked” of the close button

3. Resize the parent widget when the child removed

GOAL

Environment

Method

Appendix

GOAL

GOAL

Environment

Method

GOAL

Environment

Method

GOAL

Environment

Method

GOAL

GOAL

Environment

Method

How to change the variable size

How to change the variable width and height

Appendix

How to change the fixed size

How to change the fixed height and width.

GOAL

Environment

Related Classes

Examples

Example 1. Simple tree widget