Changing icon on inserting input in terminal in python

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I am creating a login panel in the terminal in python and I want to dynamically change icon before input i.e whenever the user fills the input the icon changes.

Example:

F:\command_line>python main.py
?  username: # initially there is a question mark.

✓ username: # If the user fills the username the icon changes to ✓

I tried:

default = '?'
onChange = '✓'
inp = input(default + " " + name + ":")
# I can't figure out how I can change it

Is it possible to do this? If so, How can I achieve it?

python-3.x shell input command-line python
1 Answers

I won't walk you through the entire thing but the link that @PranavHosangadi provided is a good resource.

It seems like you're using Windows so the curses module isn't immediately available to you. However you can pip install windows-curses to get most of the functionality. Although I have noticed some of the constants like curses.KEY_BACKSPACE differ on the windows version but you can fiddle with it and determine what works for you.

# The module you'll use
import curses

# this is the char value that backspace returns on windows
BACKSPACE = 8

# our main function
def main(stdscr):
    # this is just to initialize the input position
    inp = '? Username:'
    stdscr.addstr(1, 1, inp)
    
    # The input from the user will be assigned to 
    # this variable
    current = ''
    # our main method of obtaining user input
    # it essentially returns control after the 
    # user inputs a character
    # the return value is essentially what ord(char) returns
    # to get the actual character you can use chr(char)
    k = stdscr.getch()

    # break the loop when the x key is pressed
    while chr(k) != 'x':
        # remove characters for backspace presses
        if k == BACKSPACE:
            if len(current):
                current = current[:len(current) - 1]
        # only allow a max of 8 characters
        elif len(current) < 8:
            current = current + chr(k)
        
        # when 8 characters are entered, change the sign
        if len(current) == 8:
            inp = '✓ Username:'
        else:
            inp = '? Username:'
        
        # not clearing the screen leaves old characters in place
        stdscr.clear()
        # this enters the input on row 1, column 1
        stdscr.addstr(1, 1, inp + current)
        
        # get the next user input character
        k = stdscr.getch()

if __name__ == '__main__':
    # our function needs to be driven by curses.wrapper
    curses.wrapper(main)

Some resources:

Official Docs

Some helpful examples This one has some linux-only pieces, but with some trial and error, those parts are apparent.

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