When I was trying the exercise of TensorFlow Programming Concepts, an error “AttributeError module ‘tensorflow’ has no attribute ‘Session'” occurred.
The code run in Google Colaboratory is the following.Generic HighlightingEnlighterJS Syntax Highlighter
tf.Session can be used in tensorflow 1.x version, while it cannot be used in 2.x version.
(more…)Today’s goal is to access attributes of objects by the string of its name.
What I’d like to do is the following.
class MyClass:
class_attr = 1
def __init__(self, num):
self.attr1 = 100 + num
self.attr2 = 200 + num
def func1(self):
print("this is func1")
item = MyClass(5)
attr = "attr2"
print(item.get_attr(attr)) # output should be 205Python 3.8.7
Use getattr(object, name) to get attributes. And setattr(object, name) to set attributes.
item = MyClass(5) attr = "attr2" print(getattr(item, attr)) # output => 205
You can get methods and class variable too.
getattr(item, "func1")() # output => this is func1 print(getattr(MyClass, "class_attr")) # output => 1
Today’s goal is discuss the method of implementing bidirectional dictionary in Python.
Windows 10
Python 3.8.7
Dictionary or hash table is a data structure composed of a collection of (key, map) pair where keys are unique, which is known as an associative array, map, symbol table, or dictionary. The advantage of dictionary is its small time complexity O(1).
job_dict = {"John":"director", "Mike":"designer", "Anna":"designer", "Lisa":"engineer"}
# job_dict["Mike"] returns "designer"
Bidirectional dictionary I’d like is the dictionary that return the value when the key is given and return keys when the value is given.
# what I'd like to do
job_bidict = {"John":"director", "Mike":"designer", "Anna":"designer", "Lisa":"engineer"}
# job_bidict["Mike"] returns "designer"
# job_bidict["designer"] returns "Mike", "Anna" or ["Mike", "Anna"]I introduces 3 methods and pros and cons of them.
<!--more-->
Install and import bidict library according to bidict documentation.
pip install bidict
from bidict import bidict
job_bidict = bidict({"John":"director", "Mike":"designer", "Lisa":"engineer"}) # The values should be unique
print(job_bidict["Mike"])
# output => designer
print(job_bidict.inverse["designer"])
# output => MikeAdvantage: It’s easy to implement.
Disadvantage: The file size grows when you distribute the program.
class MyBidict:
def __init__(self, init_dict):
self.dict_normal = {} # normal dict to store (key, values)
self.dict_inverse = {} # normal dict to store (value. keys)
for key in init_dict.keys():
self.add_item(key, init_dict[key])
def add_item(self, key, value):
if key in self.dict_normal:
self.dict_normal[key].append(value)
else:
self.dict_normal[key] = [value]
if value in self.dict_inverse:
self.dict_inverse[value].append(key)
else:
self.dict_inverse[value] = [key]
def get_item(self, key):
return self.dict_normal[key]
def get_item_inverse(self, value):
return self.dict_inverse[value]
job_bidict = MyBidict({"John":"director", "Mike":"designer", "Anna":"designer", "Lisa":"engineer"})
print(job_bidict.get_item("Mike"))
# output => ['designer']
print(job_bidict.get_item_inverse("designer"))
# output => ['Mike', 'Anna']class MyBidict(dict):
def __init__(self, init_dict):
self.inverse = {}
dict.__init__(self, init_dict)
for key, value in init_dict.items():
self.inverse[value] = key
def __setitem__(self, key, value):
dict.__setitem__(self, key, value)
self.inverse.__setitem__(value, key)
job_bidict = MyBidict({"John":"director", "Mike":"designer", "Anna":"designer", "Lisa":"engineer"})
print(job_bidict["Mike"])
# output => designer
print(job_bidict.inverse["designer"])
# output => AnnaToday’s goal is to execute a function when QTreeWidgetItem is double clicked.
Windows 10
Python 3.8.7
PySide2 (5.15.2)
First I created a sample QTreeWidget as below.
import sys
from PySide2.QtWidgets import *
class MyMainWindow(QMainWindow):
def __init__(self, parent=None):
super(MyMainWindow, self).__init__(parent)
self._generate_ui()
self._init_tree_widget()
def _generate_ui(self):
main_widget = QWidget()
main_layout = QVBoxLayout()
main_widget.setLayout(main_layout)
self.setCentralWidget(main_widget)
self.tree_widget = QTreeWidget()
self.tree_widget.setSelectionMode(QAbstractItemView.ExtendedSelection)
self.tree_widget.setSelectionBehavior(QAbstractItemView.SelectItems)
main_layout.addWidget(self.tree_widget)
def _init_tree_widget(self):
headers = ["header1", "header2"]
self.tree_widget.setHeaderLabels(headers)
tree_widget_item1 = QTreeWidgetItem(["group1"])
tree_widget_item1.addChild(QTreeWidgetItem(["item1_1", "item1_2"]))
self.tree_widget.addTopLevelItem(tree_widget_item1)
tree_widget_item2 = QTreeWidgetItem(["group2"])
self.tree_widget.addTopLevelItem(tree_widget_item2)
tree_widget_item2.addChild(QTreeWidgetItem(["item2_1", "item2_2"]))
tree_widget_item2.addChild(QTreeWidgetItem(["item3_1", "item3_2"]))
def launch():
app = QApplication.instance()
if not app:
app = QApplication(sys.argv)
widget = MyMainWindow()
widget.show()
app.exec_()
launch()Connect the function to QTreeWidget.itemDoubleClicked signal.
class MyMainWindow(QMainWindow):
def __init__(self, parent=None):
# omitted
def _generate_ui(self):
main_widget = QWidget()
main_layout = QVBoxLayout()
main_widget.setLayout(main_layout)
self.setCentralWidget(main_widget)
self.tree_widget = QTreeWidget()
self.tree_widget.setSelectionMode(QAbstractItemView.ExtendedSelection)
self.tree_widget.setSelectionBehavior(QAbstractItemView.SelectItems)
self.tree_widget.itemDoubleClicked.connect(self._doubleClicked) # connect function to the signal itemDoubleClicked
main_layout.addWidget(self.tree_widget)
def _init_tree_widget(self):
# omitted
def _doubleClicked(self): # this function is executed when an item is double clicked
print("double clicked")Use QTreeWidget.currentItem(), QTreeWidget.currentColumn() or QAbstractItemView.currentIndex().
def _doubleClicked(self):
column = self.tree_widget.currentColumn()
text = self.tree_widget.currentItem().text(column)
print("double clicked item is " + text)
# output when item1_2 clicked => double clicked item is item1_2
# output when group1 clicked => double clicked item is grounp1I’d like to clear and redraw widgets in my custom PySide2 UI.
Today’s goal is to remove and delete all children widgets from the layout.
Windows 10
Python 3.8.7
PySide2 (5.15.2)
I created sample widget with clear-all button.
import sys
from PySide2.QtWidgets import *
from PySide2.QtCore import Qt, QEventLoop
class MyWidget(QWidget):
def __init__(self, parent=None):
super(MyWidget, self).__init__(parent)
self.main_layout = QVBoxLayout()
self.setLayout(self.main_layout)
self._generateUI()
def _generateUI(self):
clear_button = QPushButton("Clear All")
clear_button.clicked.connect(self._clearall)
self.main_layout.addWidget(clear_button)
label = QLabel("Label")
self.main_layout.addWidget(label)
combobox = QComboBox()
combobox.addItems(["comboBox1", "comboBox2"])
self.main_layout.addWidget(combobox)
buttons_widget = QWidget()
buttons_layout = QHBoxLayout()
buttons_widget.setLayout(buttons_layout)
for i in range(3):
button = QPushButton("button"+str(i))
buttons_layout.addWidget(button)
self.main_layout.addWidget(buttons_widget)
def _clearall(self): # the function to clear widgets
pass
if __name__ == '__main__':
app = QApplication(sys.argv)
widget = MyWidget()
widget.show()
sys.exit(app.exec_())To get the list of children in the layout, use count() and itemAt(). Because the itemAt() function returns QLayoutItem not Qwidget, we should get widget by using QLayoutItem.widget() method.
def _clearall(self):
children = []
for i in range(self.main_layout.count()):
child = self.main_layout.itemAt(i).widget()
if child:
children.append(child)
print(child)
# output
# <class 'PySide2.QtWidgets.QPushButton'>
# <class 'PySide2.QtWidgets.QLabel'>
# <class 'PySide2.QtWidgets.QComboBox'>
# <class 'PySide2.QtWidgets.QWidget'>Use deleteLater() to delete widget.
def _clearall(self):
children = []
for i in range(self.main_layout.count()):
child = self.main_layout.itemAt(i).widget()
if child:
children.append(child)
for child in children:
child.deleteLater()* 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.
There are another methods to implement _clearall() function.
It works well because the deleteLater() destroys items after returning control from the function.
def _clearall(self):
for i in range(self.main_layout.count()):
child = self.main_layout.itemAt(i).widget()
child.widget().deleteLater()This is a wrong example. The itemAt() function can’t find the child because when an item is deleted with setParent(None), other items will be renumbered.
def _clearall(self): #wrong example
for i in range(self.main_layout.count()):
child = self.main_layout.itemAt(i).widget()
child.setParent(None)
# An error occurred: AttributeError: 'NoneType' object has no attribute 'widget'You can get children of widget with children() function.
def _clearall_4(self): #wrong
for child in self.children():
print(child.__class__)
child.deleteLater()
# output
# <class 'PySide2.QtWidgets.QVBoxLayout'> # children() returns layout too
# <class 'PySide2.QtWidgets.QPushButton'>
# <class 'PySide2.QtWidgets.QLabel'>
# <class 'PySide2.QtWidgets.QComboBox'>
# <class 'PySide2.QtWidgets.QWidget'>You can get children of widget with findChild() function.
def _clearall_4(self): #wrong
for child in self.findChildren(QWidget):
print(child.__class__)
child.deleteLater()
# output
# <class 'PySide2.QtWidgets.QPushButton'>
# <class 'PySide2.QtWidgets.QLabel'>
# <class 'PySide2.QtWidgets.QComboBox'>
# <class 'PySide2.QtWidgets.QWidget'>
# <class 'PySide2.QtWidgets.QPushButton'>
# <class 'PySide2.QtWidgets.QPushButton'>
# <class 'PySide2.QtWidgets.QPushButton'>
This is a wrong example. The children() of layout returns [].
def _clearall_4(self): #wrong example
for child in self.main_layout.children():
child.deleteLator()
print("first layout children", self.main_layout.children()) # output => []Today’s goal is to create On/Off button in my PySide UI as below.
Windows 10
Python 3.8.7
PySide2 (5.15.2)
import sys
from PySide2.QtWidgets import *
class MyWidget(QWidget):
def __init__(self):
super(MyWidget, self).__init__()
self.layout = QVBoxLayout()
self.on_off_button = QPushButton("on/off Button")
self.on_off_button.setCheckable(True)
#self.layout.addWidget(self.on_off_button)
self.setLayout(self.layout)
if __name__ == '__main__':
app = QApplication(sys.argv)
widget = MyWidget()
widget.show()
sys.exit(app.exec_())
QAbstractButton has a method setCheckable().
class MyWidget(QWidget):
def __init__(self):
super(MyWidget, self).__init__()
self.layout = QVBoxLayout()
self.on_off_button = QPushButton("on/off Button")
self.on_off_button.setCheckable(True) # set Checkable True
self.layout.addWidget(self.on_off_button)
self.setLayout(self.layout)To change the status manually, use the setChecked() method of QAbstractButton.
For example, reset button can be implemented by using the function to set the button unchecked.
class MyWidget(QWidget):
def __init__(self):
super(MyWidget, self).__init__()
self.layout = QGridLayout()
self.reset_button = QPushButton("Reset")
self.reset_button.clicked.connect(self._reset)
self.layout.addWidget(self.reset_button,0,0,1,3)
self.on_off_button1 = QPushButton("on/off 1")
self.on_off_button1.setCheckable(True)
self.layout.addWidget(self.on_off_button1,1,0,1,1)
self.on_off_button2 = QPushButton("on/off 2")
self.on_off_button2.setCheckable(True)
self.layout.addWidget(self.on_off_button2,1,1,1,1)
self.on_off_button3 = QPushButton("on/off 3")
self.on_off_button3.setCheckable(True)
self.layout.addWidget(self.on_off_button3,1,2,1,1)
self.setLayout(self.layout)
def _reset(self):
self.on_off_button1.setChecked(False)
self.on_off_button2.setChecked(False)
self.on_off_button3.setChecked(False)
To get object name from the object.
Python 3.8.7
Use special attributes “__class__” of the object.
f = open('test.txt', 'r')
# getting class name
print(f.__class__.__name__)
#output => TextIOWrapper
# getting the module where the class is defined
print(f.__class__.__module__)
#output => _io
f.close()Reference: Special Attributes
To import modules by its name as below.
def import_n_th_module(index):
"""
the function to get index number and import the module named mymodule+index such as mymodule1, mymodule2,...
"""
module_name = 'mymodule' + str(index)
# import module_name => the error occuredPython 3.8.7
The purpose of the importlib package is two-fold. One is to provide the implementation of the import statement (and thus, by extension, the import() function) in Python source code. <omit>
from importlib — The implementation of import of Python documentaion
You can import module with importlib.import_module() as follows.
importlib.import_module('numpy')
# output => import numpy moduleI created 3 modules in modules package. And each module prints “[module_name] is imported” when being imported.
#test.py
import sys
import importlib
index = 3
importlib.import_module('modules.mymodule' + str(index))
# output => "mymodule3 is imported"Two, the components to implement import are exposed in this package, making it easier for users to create their own custom objects (known generically as an importer) to participate in the import process.
from importlib — The implementation of import of Python documentaion
You can see all methods of importlib in importlib — The implementation of import of Python documentaion.
This is a part of the project “Easy Keymap Generator”.
To implement a function that get keyconfig name and return keyconfig object.
The list of keyconfig names can be seen in Preferences window.
Blender 2.83 (Python 3.7.4)
Windows 10
This is my solution, but I don’t think it is the best way. Please let me know if you have any better ideas.
def get_keyconfig(keyconfig_name):
wm = bpy.context.window_manager
if keyconfig_name in wm.keyconfigs.keys():
return wm.keyconfigs[keyconfig_name]
else:
return NoneIf there is no keyconfig you’d like to get in current environment, you should activate the keyconfig by its path manually.
key_config_dict = get_keyconfig_dict()
configs = list(key_config_dict.keys())
print(configs)
# output => ['blender', 'blender_27x', 'industry_compatible', 'test1', 'test2']
kc = get_keyconfig(configs[1], key_config_dict)
print(kc)
# output => blender_27x <bpy_struct, KeyConfig("blender_27x")>I created a function to get the dict with keys of keyconfig name and values of path to the keyconfig python file.
Reference: How to get key config list in Blender Python
def get_keyconfigs():
"""
:return: dict{kerconfig_name(str): path to config file(str)}
"""
config_pathes = bpy.utils.preset_paths("keyconfig")
config_dict = {}
for config_path in config_pathes:
for file in os.listdir(config_path):
name, ext = os.path.splitext(file)
if ext.lower() in [".py", ".xml"] and not name[0] == ".":
config_dict[name] = os.path.join(config_path, file)
return config_dictActivate the specified keyconfig by its path and get active keyconfig with wm.keyconfigs.active then restore active keyconfig to original settings.
def get_keyconfig(keyconfig_name, keyconfig_dict):
wm = bpy.context.window_manager
if keyconfig_name in wm.keyconfigs.keys(): #if the keyconfig can be found, return it
return wm.keyconfigs[keyconfig_name]
else: # activate by config path and return it
keyconfig_path = keyconfig_dict[keyconfig_name]
current_path = keyconfig_dict[wm.keyconfigs.active.name]
bpy.ops.preferences.keyconfig_activate(filepath=keyconfig_path)
kc = wm.keyconfigs.active
bpy.ops.preferences.keyconfig_activate(filepath=current_path)
return kcThis is a part of the project “Easy Keymap Generator”.
To get the key config list in my addon. The list of key configs can be seen in Preferences window.
Blender 2.83 (Python 3.7.4)
Windows 10
Get the list directly from the preset directories.
Related article: How to get preset paths in Blender Python
def get_keyconfigs():
"""
:return: dict{kerconfig_name(str): path to config file(str)}
"""
config_pathes = bpy.utils.preset_paths("keyconfig")
config_dict = {}
for config_path in config_pathes:
for file in os.listdir(config_path):
name, ext = os.path.splitext(file)
if ext.lower() in [".py", ".xml"] and not name[0] == ".":
config_dict[name] = os.path.join(config_path, file)
return config_dict
print(key_config_dict.keys())
#output => dict_keys(['blender', 'blender_27x', 'industry_compatible', 'test1', 'test2'])