Category Archives: Curses

Python Curses – Custom Menu

Continuing on the same project as the previous post, I came to wanting to make a custom menu with curses in Python.  Realizing that there are functions to create menus in curses already, I wanted to build this fro m the bottom up.  The concept was to produce a menu that would highlight the selection change on the arrow keys or direct input, and then on a press of the Enter key the menu would return that selection.

Now, while writing this, you’ll see in my code that I took probable the least efficient way of building this menu, but it helps in making itself explanatory for the person learning curses.  As for the context of this coding, I built it as a function in my XFDL viewer, so there are 5 options in the menu.  I used win.keypad(0) to enable the use of the arrow keys but for some reason, the curses.KEY_UP was not being detected so the arrow key up and arrow key down are 259 and 258, respectively.  This does work though, I also have the menu catch numbers 1-5 and set the highlighted line accordingly.

def menu():
    curses.init_pair(1,curses.COLOR_RED, curses.COLOR_WHITE)
    screen.keypad(1)
    pos = 1
    x = None
    # I'm going to be lazy and save some typing here.
    h = curses.color_pair(1)
    n = curses.A_NORMAL
    while x != ord('\n'):
        # Gotta reset the screen from the root or lose the border, window, etc.
        screen.clear()
        screen.border(0)
        screen.addstr(2,2, "XFDL VIEWER", curses.A_STANDOUT)
        screen.addstr(4,2, "Please select an option...", curses.A_BOLD)
        # Detect what is highlighted by the 'pos' variable.
        if pos == 1:
            screen.addstr(5,4, "1 - XFDL -> XML",h)
        else:
            screen.addstr(5,4, "1 - XFDL -> XML",n)
        if pos == 2:
            screen.addstr(6,4, "2 - XML  -> XFDL",h)
        else:
            screen.addstr(6,4, "2 - XML  -> XFDL",n)
        if pos == 3:
            screen.addstr(7,4, "3 - Show XML",h)
        else:
            screen.addstr(7,4, "3 - Show XML",n)
        if pos == 4:
            screen.addstr(8,4, "4 - Exit",h)
        else:
            screen.addstr(8,4, "4 - Exit",n)
        if pos == 5:
            screen.addstr(9,4, "5 - DEBUG", h)
        else:
            screen.addstr(9,4, "5 - DEBUG", n)
        screen.refresh()
        x = screen.getch()
        # Is 'x' 1-5 or arrow up, arrow down?
        if x == ord('1'):
            pos = 1
        elif x == ord('2'):
            pos = 2
        elif x == ord('3'):
            pos = 3
        elif x == ord('4'):
            pos = 4
        elif x == ord('5'):
            pos = 5
        # It was a pain in the ass trying to get the arrows working.
        elif x == 258:
            if pos < 5:
                pos += 1
            else:
                pos = 1
        # Since the curses.KEY_* did not work, I used the raw return value.
        elif x == 259:
            if pos > 1:
                pos += -1
            else:
                pos = 5
        elif x != ord('\n'):
            curses.flash()
            # show_error() is my custom function for displaying a message:
            # show_error(str:message, int:line#, int:seconds_to_display)
            show_error('Invalid Key',11,1)

    return ord(str(pos))

I’ve highlighted the lines pertaining to my work around for the key pad.  This function will return the menu option and then that is processed for a reaction.  Reminder: the ‘screen’ object for my curses window is a global variable. I’m quite thrilled at the simplicity of this and the curses library, although I am disappointed in the lack of tutorials on the web deeper than typical ‘Hello World’ tutorials, but I hope these posts go to help others exploring this library!

Here’s a nice picture of the library in action:

Customize menu in action...
Be sure to comment on these tutorials and let me know if there is more detail needed or if they are helpful!!

Python Curses – Custom Progress Bar

Custom Progress BarIn making a visual editor for my XFDL project, I’ve decided to do the basic start in curses.  This is a module of python/library of C that I have not been able to utilize much at this point despite interest.  Unfortunately, there seems to be limiteexid documentation beyond the standard ‘Hello World’ type of program.  I’ll write this short tutorial with the assumption you can get through those tutorials and utilize this object.

The concept here is to create a progress bar in curses.  This example does not have any data but a basic understanding of python would allow you to create the refreshes on percentage of completion rather than time based as I have here.

def show_progress():
    #Create a window object.
    win = curses.newwin(3,32,14,10)
    # Add the Border
    win.border(0)
    # Current text: Progress
    win.addstr(1,1,"Progress ")
    # This is to move the progress bar per iteration.
    pos = 10
    # Random number I chose for demonstration.
    for i in range(15):
        # Add '.' for each iteration.
        win.addstr(1,pos,".")
        # Refresh or we'll never see it.
        win.refresh()
        # Here is where you can customize for data/percentage.
        time.sleep(0.05)
        # Need to move up or we'll just redraw the same cell!
        pos += 1
    # Current text: Progress ............... Done!
    win.addstr(1,26,"Done!")
    # Gotta show our changes.
    win.refresh()
    # Without this the bar fades too quickly for this example.
    time.sleep(0.5)

See, nothing to it.  The first line creates a new window object for and the next line adds its border.  I mapped out the relative positions for text, and you’ll want to customize this to what you need to use in your program, but for the sake of demonstration, it will show a period for each iteration.  As previously stated, you can customize this to be data or percentage driven in your program.  Don’t forget to call win.refresh() for each iteration you want to show on the screen!