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#!/usr/bin/env python3
"""Utilities related to user input."""
import logging
import signal
import sys
from typing import List
import readchar # type: ignore
import exceptions
logger = logging.getLogger(__file__)
def single_keystroke_response(
valid_responses: List[str],
*,
prompt: str = None,
default_response: str = None,
timeout_seconds: int = None,
) -> str:
"""Get a single keystroke response to a prompt."""
def _handle_timeout(signum, frame) -> None:
raise exceptions.TimeoutError()
def _single_keystroke_response_internal(
valid_responses: List[str], timeout_seconds=None
) -> str:
os_special_keystrokes = [3, 26] # ^C, ^Z
if timeout_seconds is not None:
signal.signal(signal.SIGALRM, _handle_timeout)
signal.alarm(timeout_seconds)
try:
while True:
response = readchar.readchar()
logger.debug('Keystroke: 0x%x', ord(response))
if response in valid_responses:
break
if ord(response) in os_special_keystrokes:
break
return response
finally:
if timeout_seconds is not None:
signal.alarm(0)
if prompt is not None:
print(prompt, end="")
sys.stdout.flush()
try:
response = _single_keystroke_response_internal(valid_responses, timeout_seconds)
if ord(response) == 3:
raise KeyboardInterrupt('User pressed ^C in input_utils.')
except exceptions.TimeoutError:
if default_response is not None:
response = default_response
if prompt is not None:
print(response)
return response
def yn_response(prompt: str = None, *, timeout_seconds=None) -> str:
"""Get a Y/N response to a prompt."""
return single_keystroke_response(
["y", "n", "Y", "N"], prompt=prompt, timeout_seconds=timeout_seconds
).lower()
def keystroke_helper() -> None:
"""Misc util to watch keystrokes and report what they were."""
print("Watching for keystrokes; ^C to quit.")
while True:
key = readchar.readkey()
if len(key) == 1:
print(f'That was "{key}" ({ord(key)}).')
if ord(key) == 3:
return
else:
print(f'That was sequence "{key}" (', end="")
for _ in key:
print(f" {ord(_)} ", end="")
print(")")
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