Class Reader

Lib/_pyrepl/reader.py:169–816

The Reader class implements the bare bones of a command reader, handling such details as editing and cursor motion. What it does not support are such things as completion or history support - these are implemented elsewhere. Instance variables of note include: * buffer:

@dataclass(slots=True)
class Reader:
    """The Reader class implements the bare bones of a command reader,
    handling such details as editing and cursor motion.  What it does
    not support are such things as completion or history support -
    these are implemented elsewhere.

    Instance variables of note include:

      * buffer:
        A *list* (*not* a string at the moment :-) containing all the
        characters that have been entered.
      * console:
        Hopefully encapsulates the OS dependent stuff.
      * pos:
        A 0-based index into `buffer' for where the insertion point
        is.
      * screeninfo:
        Ahem.  This list contains some info needed to move the
        insertion point around reasonably efficiently.
      * cxy, lxy:
        the position of the insertion point in screen ...
      * syntax_table:
        Dictionary mapping characters to `syntax class'; read the
        emacs docs to see what this means :-)
      * commands:
        Dictionary mapping command names to command classes.
      * arg:
        The emacs-style prefix argument.  It will be None if no such
        argument has been provided.
      * dirty:
        True if we need to refresh the display.
      * kill_ring:
        The emacs-style kill-ring; manipulated with yank & yank-pop
      * ps1, ps2, ps3, ps4:
        prompts.  ps1 is the prompt for a one-line input; for a
        multiline input it looks like:
            ps2> first line of input goes here
            ps3> second and further
            ps3> lines get ps3
            ...
            ps4> and the last one gets ps4
        As with the usual top-level, you can set these to instances if
        you like; str() will be called on them (once) at the beginning
        of each command.  Don't put really long or newline containing
        strings here, please!
        This is just the default policy; you can change it freely by
        overriding get_prompt() (and indeed some standard subclasses
        do).
      * finished:
        handle1 will set this to a true value if a command signals
        that we're done.
    """

    console: console.Console

    ## state
    buffer: list[str] = field(default_factory=list)
    pos: int = 0