You can have it done by reading the input and converting the scancodes using the built-in KEY_* constants of the global scope.
Simple code snippet would look like this:
func _ready():
set_process_input(true)
func _input(event):
if event.type == InputEvent.KEY and event.is_pressed():
print('pressed: ' + str(event.unicode))
if event.scancode == KEY_A:
print('AHA!')
As far as I know there's no direct way to convert scancodes to string, so you can create a dictionary like {scancode: 'string'} to convert symbols.