We create TUI on python
Hi, Habr! In this article I will talk about npyscreen - a library for creating text interfaces for terminal and console applications.
Installation
The package is available for download via PyPI.
sudo pip3 install npyscreen Types of objects
Npyscreen uses 3 main types of objects:
- Application objects - provide start and end of the application, creation of forms, event handling.
Mainly used by NPSAppManaged and StandardApp (with event support). - Form objects - the area of ​​the screen that contains the widgets.
Basic forms:- FormBaseNew is an empty form.
- Form - the form with the “ok” button.
- ActionForm is a form with two buttons: “ok” and “cancel”.
- FormWithMenus - a form that supports the work with the menu.
- Widget Objects - various elements located on forms.
Some widgets:- Textfield , PasswordEntry , MultiLineEdit , FilenameCombo * - data entry forms.
- DateCombo , ComboBox , FilenameCombo - drop-down lists.
- MultiSelect , MultiSelect , BufferPager - widgets with a choice.
- Slider , TitleSlider - sliders.
More information can be found on the official website with documentation .
Write Hello World
Forms are convenient for creating, inheriting them from the built-in classes. Thus, you can override the built-in methods to extend the functionality of the application.
#!/usr/bin/env python3 import npyscreen class App(npyscreen.StandardApp): def onStart(self): self.addForm("MAIN", MainForm, name="Hello Habr!") class MainForm(npyscreen.ActionForm): # def create(self): # TitleText self.title = self.add(npyscreen.TitleText, name="TitleText", value="Hello World!") # , «ok» def on_ok(self): self.parentApp.setNextForm(None) # , «cancel» def on_cancel(self): self.title.value = "Hello World!" MyApp = App() MyApp.run() 
Arrangement of elements
By default, widgets take up as much space as possible.
To set the exact coordinates, you need to set the parameters:
- relx , rely - the position of the widget relative to the origin of the form.
- width , height , max_width , max_height - limiting the size of the widget.
#!/usr/bin/env python3 import npyscreen class App(npyscreen.StandardApp): def onStart(self): self.addForm("MAIN", MainForm, name="Hello Habr!") class MainForm(npyscreen.FormBaseNew): def create(self): # y, x = self.useable_space() self.add(npyscreen.TitleDateCombo, name="Date:", max_width=x // 2) self.add(npyscreen.TitleMultiSelect, relx=x // 2 + 1, rely=2, value=[1, 2], name="Pick Several", values=["Option1", "Option2", "Option3"], scroll_exit=True) # self.add(npyscreen.TitleFilename, name="Filename:", rely=-5) MyApp = App() MyApp.run() 
Boxes and custom colors
It is simple to make a wrapper in the form of a box - you need to create a class inherited from BoxTitle and redefine the _contained_widget attribute, putting the widget that will be inside there.
There are several built-in color themes available in npyscreen . If you wish, you can add your own. You can set them using the setTheme method.
Setting the text color is a bit more complicated. I had to expand the functionality of the library to make it work.
#!/usr/bin/env python3 from src import npyscreen import random class App(npyscreen.StandardApp): def onStart(self): # . DefaultTheme npyscreen.setTheme(npyscreen.Themes.ColorfulTheme) self.addForm("MAIN", MainForm, name="Hello Habr!") class InputBox(npyscreen.BoxTitle): # MultiLineEdit _contained_widget = npyscreen.MultiLineEdit class MainForm(npyscreen.FormBaseNew): def create(self): y, x = self.useable_space() obj = self.add(npyscreen.BoxTitle, name="BoxTitle", custom_highlighting=True, values=["first line", "second line"], rely=y // 4, max_width=x // 2 - 5, max_height=y // 2) self.add(InputBox, name="Boxed MultiLineEdit", footer="footer", relx=x // 2, rely=2) color1 = self.theme_manager.findPair(self, 'GOOD') color2 = self.theme_manager.findPair(self, 'WARNING') color3 = self.theme_manager.findPair(self, 'NO_EDIT') color_list = [color1, color2, color3] first_line_colors = [random.choice(color_list) for i in range(len("first line"))] second_line_colors = [random.choice(color_list) for i in range(len("second"))] # obj.entry_widget.highlighting_arr_color_data = [first_line_colors, second_line_colors] MyApp = App() MyApp.run() 
')
Events and event handlers
The StandardApp class in npyscreen supports an event queue.
The add_handlers method is used as click processing.
#!/usr/bin/env python3 import npyscreen import curses class App(npyscreen.StandardApp): def onStart(self): self.addForm("MAIN", MainForm, name="Hello Habr!") class InputBox1(npyscreen.BoxTitle): _contained_widget = npyscreen.MultiLineEdit def when_value_edited(self): self.parent.parentApp.queue_event(npyscreen.Event("event_value_edited")) class InputBox2(npyscreen.BoxTitle): _contained_widget = npyscreen.MultiLineEdit class MainForm(npyscreen.FormBaseNew): def create(self): self.add_event_hander("event_value_edited", self.event_value_edited) new_handlers = { # ctrl+Q "^Q": self.exit_func, # alt+enter inputbox curses.ascii.alt(curses.ascii.NL): self.inputbox_clear } self.add_handlers(new_handlers) y, x = self.useable_space() self.InputBox1 = self.add(InputBox1, name="Editable", max_height=y // 2) self.InputBox2 = self.add(InputBox2, footer="No editable", editable=False) def event_value_edited(self, event): self.InputBox2.value = self.InputBox1.value self.InputBox2.display() def inputbox_clear(self, _input): self.InputBox1.value = self.InputBox2.value = "" self.InputBox1.display() self.InputBox2.display() def exit_func(self, _input): exit(0) MyApp = App() MyApp.run() 
References:
Official documentation
Original source codes
The repository I updated (the main githab seems to be dead)
Telegram client on npyscreen (which is on the first screenshot)
Source: https://habr.com/ru/post/352904/
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