Can't check what button is pressed in pynput-CodePudding

I have problem with Keys in pynput

on_press function should check if button pressed i 'h' but it gives error

from pynput.keyboard import Key, Listener


def on_press(key):
    print(key)
    if key == Key.h:
        print('done')


def on_release(key):
    print('{0} release'.format(key))
    if key == Key.esc:
        return False


# Collect events until released
with Listener(
        on_press=on_press,
        on_release=on_release) as listener:
    listener.join()

CodePudding user response：

the error is created by the if key == Key.h: statement inside the on_press function. When i comment this out, it works without error.

So this works:

from pynput.keyboard import Key, Listener


def on_press(key):
    print(key)
    # if key == Key.h:    # <-- cause the error
    #     print('done')  # <-- cause the error


def on_release(key):
    print('{0} release'.format(key))
    if key == Key.esc:
        return False


# Collect events until released
with Listener(
        on_press=on_press,
        on_release=on_release) as listener:
    listener.join()

returns (when i press various buttons etc):

'h'
'h' release
Key.alt_l
Key.tab
Key.alt_l release
Key.tab release
Key.alt_l
Key.tab
Key.alt_l release

It looks like the examples use a try-except block for the equivalent on_press function that you have created.

Here is the link to how it works: https://pynput.readthedocs.io/en/latest/keyboard.html

When i replace the function with this is performs well:

def on_press(key):
    print(key)
    try:
        if key == Key.h:
            print('done')
    except:
        print('something else')

and i get this:

'h'
something else
'h' release
'i'
something else
'i' release
Key.alt_l
something else
Key.tab
something else
Key.alt_l release
Key.tab release
Key.alt_l

You can see that the exception needs to be handled (many time) from the above, which is why the code in the question was broken.

CodePudding user response：

your way to solve this problem doesn't work or maybe it's mine misunderstanding. When i tried to comment every print, to only print 'done' after checking if pressed key is 'h' it doesn't work

def on_press(key):
    try:
        if key == Key.h:
            print('done')
    except:
        return


def on_release(key):
    #print('{0} release'.format(key))
    if key == Key.esc:
        return False