Python curses example

pycurses.py

import sys,os
import curses

def draw_menu(stdscr):
    k = 0
    cursor_x = 0
    cursor_y = 0

    # Clear and refresh the screen for a blank canvas
    stdscr.clear()
    stdscr.refresh()

    # Start colors in curses
    curses.start_color()
    curses.init_pair(1, curses.COLOR_CYAN, curses.COLOR_BLACK)
    curses.init_pair(2, curses.COLOR_RED, curses.COLOR_BLACK)
    curses.init_pair(3, curses.COLOR_BLACK, curses.COLOR_WHITE)

    # Loop where k is the last character pressed
    while (k != ord('q')):

        # Initialization
        stdscr.clear()
        height, width = stdscr.getmaxyx()

        if k == curses.KEY_DOWN:
            cursor_y = cursor_y + 1
        elif k == curses.KEY_UP:
            cursor_y = cursor_y - 1
        elif k == curses.KEY_RIGHT:
            cursor_x = cursor_x + 1
        elif k == curses.KEY_LEFT:
            cursor_x = cursor_x - 1

        cursor_x = max(0, cursor_x)
        cursor_x = min(width-1, cursor_x)

        cursor_y = max(0, cursor_y)
        cursor_y = min(height-1, cursor_y)

        # Declaration of strings
        title = "Curses example"[:width-1]
        subtitle = "Written by Clay McLeod"[:width-1]
        keystr = "Last key pressed: {}".format(k)[:width-1]
        statusbarstr = "Press 'q' to exit | STATUS BAR | Pos: {}, {}".format(cursor_x, cursor_y)
        if k == 0:
            keystr = "No key press detected..."[:width-1]

        # Centering calculations
        start_x_title = int((width // 2) - (len(title) // 2) - len(title) % 2)
        start_x_subtitle = int((width // 2) - (len(subtitle) // 2) - len(subtitle) % 2)
        start_x_keystr = int((width // 2) - (len(keystr) // 2) - len(keystr) % 2)
        start_y = int((height // 2) - 2)

        # Rendering some text
        whstr = "Width: {}, Height: {}".format(width, height)
        stdscr.addstr(0, 0, whstr, curses.color_pair(1))

        # Render status bar
        stdscr.attron(curses.color_pair(3))
        stdscr.addstr(height-1, 0, statusbarstr)
        stdscr.addstr(height-1, len(statusbarstr), " " * (width - len(statusbarstr) - 1))
        stdscr.attroff(curses.color_pair(3))

        # Turning on attributes for title
        stdscr.attron(curses.color_pair(2))
        stdscr.attron(curses.A_BOLD)

        # Rendering title
        stdscr.addstr(start_y, start_x_title, title)

        # Turning off attributes for title
        stdscr.attroff(curses.color_pair(2))
        stdscr.attroff(curses.A_BOLD)

        # Print rest of text
        stdscr.addstr(start_y + 1, start_x_subtitle, subtitle)
        stdscr.addstr(start_y + 3, (width // 2) - 2, '-' * 4)
        stdscr.addstr(start_y + 5, start_x_keystr, keystr)
        stdscr.move(cursor_y, cursor_x)

        # Refresh the screen
        stdscr.refresh()

        # Wait for next input
        k = stdscr.getch()

def main():
    curses.wrapper(draw_menu)

if __name__ == "__main__":
    main()

I also thank Clay for his very nice code example. I took it on myself to improve it a little by adding code to more cleanly clear out the keycode line(s) and to get all three curses "key read" functions to show the results for getch(), get_wch() and getkey() all for the same single keystroke entered.

Copy pasted below if anyone is interested.

Edit: After seeing unexpected failures of the getkey() code on Linux systems using the ncursesw library (though it never failed on Windows systems using the PDCurses library underneath) , I asked for some help on the bug-ncurses mailing list, and discovered that the unget_wch() function does not know what to do with a non-character (i.e., arrow keys, Home, End, F1, etc.). Instead, if get_wch() returns an integer representing one of those "non-printing" keys, you must use ungetch() to put that key back in order for a subsequent getkey() or get_wch() to be able to retrieve it again.

I have updated the code below to reflect that technique.

Peter

import curses

def draw_menu(stdscr):
    k = 0
    kw = 0
    kk = ""
    height, width = stdscr.getmaxyx()
    min_x_keystr = width - 1
    min_x_wkeystr = width - 1
    min_x_kkeystr = width - 1
    cursor_x = 0
    cursor_y = 0

    # Clear and refresh the screen for a blank canvas
    stdscr.clear()
    stdscr.refresh()

    # Start colors in curses
    curses.start_color()
    curses.init_pair(1, curses.COLOR_CYAN, curses.COLOR_BLACK)
    curses.init_pair(2, curses.COLOR_RED, curses.COLOR_BLACK)
    curses.init_pair(3, curses.COLOR_BLACK, curses.COLOR_WHITE)

    # Loop where k is the last character pressed
    while (k != ord('q')):

        # Initialization
        #stdscr.clear()
        height, width = stdscr.getmaxyx()

        if k == curses.KEY_DOWN:
            cursor_y = cursor_y + 1
        elif k == curses.KEY_UP:
            cursor_y = cursor_y - 1
        elif k == curses.KEY_RIGHT:
            cursor_x = cursor_x + 1
        elif k == curses.KEY_LEFT:
            cursor_x = cursor_x - 1

        cursor_x = max(0, cursor_x)
        cursor_x = min(width-1, cursor_x)

        cursor_y = max(0, cursor_y)
        cursor_y = min(height-1, cursor_y)

        # Declaration of strings
        title = "Curses example"[:width-1]
        subtitle = "Written by Clay McLeod"[:width-1]
        statusbarstr = "Press 'q' to exit | STATUS BAR | Pos: {}, {}".format(cursor_x, cursor_y)
        if k == 0:
            keystr = "No key press detected..."[:width-1]
        else:
            keystr = "Last key pressed: {}".format(k)[:width-1]
        if kw == 0:
            wkeystr = "No wide key press detected..."[:width-1]
        else:
            wkeystr = "Last wide key pressed: {}".format(kw)[:width-1]
        if kk == 0:
            kkeystr = "No 'key' press detected..."[:width-1]
        else:
            kkeystr = "Last 'key' pressed: {}".format(kk)[:width-1]

        # Centering calculations
        start_x_title = int((width // 2) - (len(title) // 2) - len(title) % 2)
        start_x_subtitle = int((width // 2) - (len(subtitle) // 2) - len(subtitle) % 2)
        start_x_keystr = int((width // 2) - (len(keystr) // 2) - len(keystr) % 2)
        start_x_wkeystr = int((width // 2) - (len(wkeystr) // 2) - len(wkeystr) % 2)
        start_x_kkeystr = int((width // 2) - (len(kkeystr) // 2) - len(kkeystr) % 2)
        start_y = int((height // 2) - 2)
        min_x_keystr = min(min_x_keystr, start_x_keystr)
        min_x_wkeystr = min(min_x_wkeystr, start_x_wkeystr)
        min_x_kkeystr = min(min_x_kkeystr, start_x_kkeystr)

        # Rendering some text
        whstr = "Width: {}, Height: {}".format(width, height)
        stdscr.addstr(0, 0, whstr, curses.color_pair(1))

        # Render status bar
        stdscr.attron(curses.color_pair(3))
        stdscr.addstr(height-1, 0, statusbarstr)
        stdscr.addstr(height-1, len(statusbarstr), " " * (width - len(statusbarstr) - 1))
        stdscr.attroff(curses.color_pair(3))

        # Turning on attributes for title
        stdscr.attron(curses.color_pair(2))
        stdscr.attron(curses.A_BOLD)

        # Rendering title
        stdscr.addstr(start_y, start_x_title, title)

        # Turning off attributes for title
        stdscr.attroff(curses.color_pair(2))
        stdscr.attroff(curses.A_BOLD)

        # Print rest of text
        stdscr.addstr(start_y + 1, start_x_subtitle, subtitle)
        stdscr.addstr(start_y + 3, (width // 2) - 2, '-' * 4)
        stdscr.addstr(start_y + 5, start_x_keystr, keystr)
        stdscr.addstr(start_y + 7, start_x_wkeystr, wkeystr)
        stdscr.addstr(start_y + 9, start_x_kkeystr, kkeystr)
        stdscr.move(cursor_y, cursor_x)

        # Refresh the screen
        stdscr.refresh()

        # Wait for next input
        k = stdscr.getch()

        # Get wide-char version
        curses.ungetch(k)
        kw = stdscr.get_wch()

        # Get key version
        if isinstance(kw, str):
            curses.unget_wch(kw)
        else:
            curses.ungetch(kw)
        kk = stdscr.getkey()

        # Clear the keystroke text
        stdscr.move(start_y + 5, min_x_keystr)
        stdscr.clrtoeol()
        stdscr.move(start_y + 7, min_x_wkeystr)
        stdscr.clrtoeol()
        stdscr.move(start_y + 9, min_x_kkeystr)
        stdscr.clrtoeol()
        stdscr.refresh()

def main():
    curses.wrapper(draw_menu)

if __name__ == "__main__":
    main()

To get less flickering, use stdscr.erase() instead of stdscr.clear(), see this S.O answer.

Thank you!

Thank you for the code. When ran in the terminal, it does good to represent some of the major functionalities of the curses library 👍

Thanks!

Thank you!

Thank you for great example.

thanks

thank you.

why do you have the import for sys, and os if you don't use them in your code?

I added stdscr.keypad(True) to make the cursor move.

great little snippet, I just tested it with the latest termux build from github on android and it works great.

very nice!