More about key bindings¶
This page contains a few additional notes about key bindings.
Key bindings can be defined as follows by creating a
from prompt_toolkit.key_binding import KeyBindings bindings = KeyBindings() @bindings.add('a') def _(event): " Do something if 'a' has been pressed. " ... @bindings.add('c-t') def _(event): " Do something if Control-T has been pressed. " ...
c-q (control-q) and c-s (control-s) are often captured by the terminal, because they were used traditionally for software flow control. When this is enabled, the application will automatically freeze when c-s is pressed, until c-q is pressed. It won’t be possible to bind these keys.
In order to disable this, execute the following command in your shell, or even add it to your .bashrc.
Key bindings can even consist of a sequence of multiple keys. The binding is only triggered when all the keys in this sequence are pressed.
@bindings.add('a', 'b') def _(event): " Do something if 'a' is pressed and then 'b' is pressed. " ...
If the user presses only a, then nothing will happen until either a second key (like b) has been pressed or until the timeout expires (see later).
List of special keys¶
Besides literal characters, any of the following keys can be used in a key binding:
|Escape Shift + escape||escape s-escape|
|Arrows||left, right, up, down|
|Navigation||home, end, delete, pageup, pagedown, insert|
c-a, c-b, c-c, c-d, c-e, c-f, c-g, c-h, c-i, c-j, c-k, c-l,
c-m, c-n, c-o, c-p, c-q, c-r, c-s, c-t, c-u, c-v, c-w, c-x,
|Control + number||c-1, c-2, c-3, c-4, c-5, c-6, c-7, c-8, c-9, c-0|
|Control + arrow||c-left, c-right, c-up, c-down|
|Other control keys||c-@, c-\, c-], c-^, c-_, c-delete|
|Shift + arrow||s-left, s-right, s-up, s-down|
|Control + Shift + arrow||c-s-left, c-s-right, c-s-up, c-s-down|
|Other shift keys||s-delete, s-tab|
f1, f2, f3, f4, f5, f6, f7, f8, f9, f10, f11, f12,
f13, f14, f15, f16, f17, f18, f19, f20, f21, f22, f23, f24
There are a couple of useful aliases as well:
Note that the supported keys are limited to what typical VT100 terminals offer. Binding c-7 (control + number 7) for instance is not supported.
Binding alt+something, option+something or meta+something¶
Vt100 terminals translate the alt key into a leading escape key. For instance, in order to handle alt-f, we have to handle escape + f. Notice that we receive this as two individual keys. This means that it’s exactly the same as first typing escape and then typing f. Something this alt-key is also known as option or meta.
In code that looks as follows:
@bindings.add('escape', 'f') def _(event): " Do something if alt-f or meta-f have been pressed. "
Sometimes you want to catch any key that follows after a certain key stroke. This is possible by binding the ‘<any>’ key:
@bindings.add('a', '<any>') def _(event): ...
This will handle aa, ab, ac, etcetera. The key binding can check the event object for which keys exactly have been pressed.
Attaching a filter (condition)¶
In order to enable a key binding according to a certain condition, we have to
pass it a
Filter, usually a
Condition instance. (Read more about
from prompt_toolkit.filters import Condition @Condition def is_active(): " Only activate key binding on the second half of each minute. " return datetime.datetime.now().second > 30 @bindings.add('c-t', filter=is_active) def _(event): # ... pass
The key binding will be ignored when this condition is not satisfied.
ConditionalKeyBindings: Disabling a set of key bindings¶
Sometimes you want to enable or disable a whole set of key bindings according
to a certain condition. This is possible by wrapping it in a
from prompt_toolkit.key_binding import ConditionalKeyBindings @Condition def is_active(): " Only activate key binding on the second half of each minute. " return datetime.datetime.now().second > 30 bindings = ConditionalKeyBindings( key_bindings=my_bindings, filter=is_active)
If the condition is not satisfied, all the key bindings in my_bindings above will be ignored.
Merging key bindings¶
Sometimes you have different parts of your application generate a collection of
key bindings. It is possible to merge them together through the
merge_key_bindings() function. This is
preferred above passing a
object around and having everyone populate it.
from prompt_toolkit.key_binding import merge_key_bindings bindings = merge_key_bindings([ bindings1, bindings2, ])
Usually not required, but if ever you have to override an existing key binding, the eager flag can be useful.
Suppose that there is already an active binding for ab and you’d like to add a second binding that only handles a. When the user presses only a, prompt_toolkit has to wait for the next key press in order to know which handler to call.
By passing the eager flag to this second binding, we are actually saying that prompt_toolkit shouldn’t wait for longer matches when all the keys in this key binding are matched. So, if a has been pressed, this second binding will be called, even if there’s an active ab binding.
@bindings.add('a', 'b') def binding_1(event): ... @bindings.add('a', eager=True) def binding_2(event): ...
This is mainly useful in order to conditionally override another binding.
Key binding handlers can be asyncio coroutines.
from prompt_toolkit.application import in_terminal @bindings.add('x') async def print_hello(event): """ Pressing 'x' will print 5 times "hello" in the background above the prompt. """ for i in range(5): # Print hello above the current prompt. async with in_terminal(): print('hello') # Sleep, but allow further input editing in the meantime. await asyncio.sleep(1)
If the user accepts the input on the prompt, while this coroutine is not yet finished , an asyncio.CancelledError exception will be thrown in this coroutine.
There are two timeout settings that effect the handling of keys.
Application.ttimeoutlen: Like Vim’s ttimeoutlen option. When to flush the input (For flushing escape keys.) This is important on terminals that use vt100 input. We can’t distinguish the escape key from for instance the left-arrow key, if we don’t know what follows after “x1b”. This little timer will consider “x1b” to be escape if nothing did follow in this time span. This seems to work like the ttimeoutlen option in Vim.
KeyProcessor.timeoutlen: like Vim’s timeoutlen option. This can be None or a float. For instance, suppose that we have a key binding AB and a second key binding A. If the uses presses A and then waits, we don’t handle this binding yet (unless it was marked ‘eager’), because we don’t know what will follow. This timeout is the maximum amount of time that we wait until we call the handlers anyway. Pass None to disable this timeout.
Both Emacs and Vi mode allow macro recording. By default, all key presses are recorded during a macro, but it is possible to exclude certain keys by setting the record_in_macro parameter to False:
@bindings.add('c-t', record_in_macro=False) def _(event): # ... pass
Creating new Vi text objects and operators¶
We tried very hard to ship prompt_toolkit with as many as possible Vi text objects and operators, so that text editing feels as natural as possible to Vi users.
If you wish to create a new text object or key binding, that is actually possible. Check the custom-vi-operator-and-text-object.py example for more information.
The SIGINT Unix signal can be handled by binding
<sigint>. For instance:
@bindings.add('<sigint>') def _(event): # ... pass
This will handle a SIGINT that was sent by an external application into the
process. Handling control-c should be done by binding
c-c. (The terminal
input is set to raw mode, which means that a
c-c won’t be translated into a
PromptSession, there is a default binding for
c-c: it will exit the prompt, raising a
GNU readline can be configured using an .inputrc configuration file. This file contains key bindings as well as certain settings. Right now, prompt_toolkit doesn’t support .inputrc, but it should be possible in the future.