Python click 模块，getchar() 实例源码

def prompt_overwrite(file_name):
    # Skip if file doesn't exist
    if not os.path.exists(file_name):
        return True

    # Prompt for file overwrite if outfile already exists
    fmt = "File ({}) already exists. Do you want to overwrite? (y/n): "
    message = fmt.format(file_name)

    click.secho(message, nl=False, fg="red")
    choice = click.getchar()
    click.echo()

    if choice not in ("y", "Y"):
        return False

    return True

def getch():
        mainKeyCode = click.getchar()
        if mainKeyCode == KeyboardWork.EXT_KEY_PREFIX:        
            extendedKeyCode = click.getchar()
            return mainKeyCode, extendedKeyCode
        extendedKeyCode = None        
        return (mainKeyCode, extendedKeyCode)

def view(visualization_path, index_extension):
    # Guard headless envs from having to import anything large
    import sys
    if not os.getenv("DISPLAY") and sys.platform != "darwin":
        raise click.UsageError(
            'Visualization viewing is currently not supported in headless '
            'environments. You can view Visualizations (and Artifacts) at '
            'https://view.qiime2.org, or move the Visualization to an '
            'environment with a display and view it with `qiime tools view`.')

    import zipfile
    import qiime2.sdk

    if index_extension.startswith('.'):
        index_extension = index_extension[1:]
    try:
        visualization = qiime2.sdk.Visualization.load(visualization_path)
    # TODO: currently a KeyError is raised if a zipped file that is not a
    # QIIME 2 result is passed. This should be handled better by the framework.
    except (zipfile.BadZipFile, KeyError, TypeError):
        raise click.BadParameter(
            '%s is not a QIIME 2 Visualization. Only QIIME 2 Visualizations '
            'can be viewed.' % visualization_path)

    index_paths = visualization.get_index_paths(relative=False)

    if index_extension not in index_paths:
        raise click.BadParameter(
            'No index %s file with is present in the archive. Available index '
            'extensions are: %s' % (index_extension,
                                    ', '.join(index_paths.keys())))
    else:
        index_path = index_paths[index_extension]
        launch_status = click.launch(index_path)
        if launch_status != 0:
            click.echo('Viewing visualization failed while attempting to '
                       'open %s' % index_path, err=True)
        else:
            while True:
                click.echo(
                    "Press the 'q' key, Control-C, or Control-D to quit. This "
                    "view may no longer be accessible or work correctly after "
                    "quitting.", nl=False)
                # There is currently a bug in click.getchar where translation
                # of Control-C and Control-D into KeyboardInterrupt and
                # EOFError (respectively) does not work on Python 3. The code
                # here should continue to work as expected when the bug is
                # fixed in Click.
                #
                # https://github.com/pallets/click/issues/583
                try:
                    char = click.getchar()
                    click.echo()
                    if char in {'q', '\x03', '\x04'}:
                        break
                except (KeyboardInterrupt, EOFError):
                    break