# `readline` --- GNU readline のインターフェース

`readline` モジュールでは、補完や Python インタプリタからの履歴ファイルの読み書きを容易にするための多くの関数を定義しています。 このモジュールは直接、または `rlcompleter` モジュールを介して使うことができます。 `rlcompleter` モジュールは対話的プロンプトで Python 識別子の補完をサポートするものです。 このモジュールで利用される設定は、インタプリタの対話プロンプトならびに組み込みの `input()` 関数の両方の挙動に影響します。

readline のキーバインディングは初期化ファイルで設定できます。 このファイルは、たいていはホームディレクトリに `.inputrc` という名前で置いてあります。 GNU Readline マニュアルの Readline Init File を参照して、そのファイルの形式や可能な構成、 Readline ライブラリ全体の機能を知ってください。

注釈

The underlying Readline library API may be implemented by the `libedit` library instead of GNU readline. On macOS the `readline` module detects which library is being used at run time.

The configuration file for `libedit` is different from that of GNU readline. If you programmatically load configuration strings you can check for the text "libedit" in `readline.__doc__` to differentiate between GNU readline and libedit.

If you use editline/`libedit` readline emulation on macOS, the initialization file located in your home directory is named `.editrc`. For example, the following content in `~/.editrc` will turn ON vi keybindings and TAB completion:

    python:bind -v
    python:bind ^I rl_complete

Also note that different libraries may use different history file formats. When switching the underlying library, existing history files may become unusable.

## 初期化ファイル

以下の関数は初期化ファイルならびにユーザ設定関連のものです:

readline.parse_and_bind(string)

  Execute the init line provided in the string argument. This calls `rl_parse_and_bind()` in the underlying library.

readline.read_init_file([filename])

  Execute a readline initialization file. The default filename is the last filename used. This calls `rl_read_init_file()` in the underlying library.

## 行バッファ

以下の関数は行バッファを操作します:

readline.get_line_buffer()

  Return the current contents of the line buffer (`rl_line_buffer` in the underlying library).

readline.insert_text(string)

  Insert text into the line buffer at the cursor position. This calls `rl_insert_text()` in the underlying library, but ignores the return value.

readline.redisplay()

  Change what's displayed on the screen to reflect the current contents of the line buffer. This calls `rl_redisplay()` in the underlying library.

## 履歴ファイル

以下の関数は履歴ファイルを操作します:

readline.read_history_file([filename])

  Load a readline history file, and append it to the history list. The default filename is `~/.history`. This calls `read_history()` in the underlying library.

readline.write_history_file([filename])

  Save the history list to a readline history file, overwriting any existing file. The default filename is `~/.history`. This calls `write_history()` in the underlying library.

readline.append_history_file(nelements[, filename])

  Append the last nelements items of history to a file. The default filename is `~/.history`. The file must already exist. This calls `append_history()` in the underlying library. This function only exists if Python was compiled for a version of the library that supports it.

  Added in version 3.5.

readline.get_history_length()
readline.set_history_length(length)

  Set or return the desired number of lines to save in the history file. The `write_history_file()` function uses this value to truncate the history file, by calling `history_truncate_file()` in the underlying library. Negative values imply unlimited history file size.

## 履歴リスト

以下の関数はグローバルな履歴リストを操作します:

readline.clear_history()

  Clear the current history. This calls `clear_history()` in the underlying library. The Python function only exists if Python was compiled for a version of the library that supports it.

readline.get_current_history_length()

  履歴に現在ある項目の数を返します。 (`get_history_length()` は履歴ファイルに書かれる最大行数を返します。)

readline.get_history_item(index)

  Return the current contents of history item at index. The item index is one-based. This calls `history_get()` in the underlying library.

readline.remove_history_item(pos)

  Remove history item specified by its position from the history. The position is zero-based. This calls `remove_history()` in the underlying library.

readline.replace_history_item(pos, line)

  Replace history item specified by its position with line. The position is zero-based. This calls `replace_history_entry()` in the underlying library.

readline.add_history(line)

  Append line to the history buffer, as if it was the last line typed. This calls `add_history()` in the underlying library.

readline.set_auto_history(enabled)

  Enable or disable automatic calls to `add_history()` when reading input via readline. The enabled argument should be a Boolean value that when true, enables auto history, and that when false, disables auto history.

  Added in version 3.6.

  CPython 実装の詳細: Auto history is enabled by default, and changes to this do not persist across multiple sessions.

## 開始フック

readline.set_startup_hook([function])

  Set or remove the function invoked by the `rl_startup_hook` callback of the underlying library. If function is specified, it will be used as the new hook function; if omitted or `None`, any function already installed is removed. The hook is called with no arguments just before readline prints the first prompt.

readline.set_pre_input_hook([function])

  Set or remove the function invoked by the `rl_pre_input_hook` callback of the underlying library. If function is specified, it will be used as the new hook function; if omitted or `None`, any function already installed is removed. The hook is called with no arguments after the first prompt has been printed and just before readline starts reading input characters. This function only exists if Python was compiled for a version of the library that supports it.

## 補完

The following functions relate to implementing a custom word completion function. This is typically operated by the Tab key, and can suggest and automatically complete a word being typed. By default, Readline is set up to be used by `rlcompleter` to complete Python identifiers for the interactive interpreter. If the `readline` module is to be used with a custom completer, a different set of word delimiters should be set.

readline.set_completer([function])

  completer 関数を設定または削除します。function が指定された場合、新たな completer 関数として用いられます; 省略された場合や `None` の場合、現在インストールされている completer 関数は削除されます。completer 関数は `function(text, state)` の形式で、関数が文字列でない値を返すまで state を `0`, `1`, `2`, ..., にして呼び出します。この関数は text から始まる補完結果として次に来そうなものを返さなければなりません。

  The installed completer function is invoked by the entry_func callback passed to `rl_completion_matches()` in the underlying library. The text string comes from the first parameter to the `rl_attempted_completion_function` callback of the underlying library.

readline.get_completer()

  completer 関数を取得します。completer 関数が設定されていなければ `None` を返します。

readline.get_completion_type()

  Get the type of completion being attempted. This returns the `rl_completion_type` variable in the underlying library as an integer.

readline.get_begidx()
readline.get_endidx()

  Get the beginning or ending index of the completion scope. These indexes are the start and end arguments passed to the `rl_attempted_completion_function` callback of the underlying library. The values may be different in the same input editing scenario based on the underlying C readline implementation. Ex: libedit is known to behave differently than libreadline.

readline.set_completer_delims(string)
readline.get_completer_delims()

  Set or get the word delimiters for completion. These determine the start of the word to be considered for completion (the completion scope). These functions access the `rl_completer_word_break_characters` variable in the underlying library.

readline.set_completion_display_matches_hook([function])

  Set or remove the completion display function. If function is specified, it will be used as the new completion display function; if omitted or `None`, any completion display function already installed is removed. This sets or clears the `rl_completion_display_matches_hook` callback in the underlying library. The completion display function is called as `function(substitution, [matches], longest_match_length)` once each time matches need to be displayed.

## 使用例

以下の例では、ユーザのホームディレクトリにある履歴ファイル `.python_history` の読み込みと保存を自動的に行うために、 `readline` モジュールの履歴の読み書き関数をどのように使うかを示しています。以下のソースコードは通常、対話セッション中はユーザの `PYTHONSTARTUP` ファイルから自動的に実行されます:

    import atexit
    import os
    import readline

    histfile = os.path.join(os.path.expanduser("~"), ".python_history")
    try:
        readline.read_history_file(histfile)
        # default history len is -1 (infinite), which may grow unruly
        readline.set_history_length(1000)
    except FileNotFoundError:
        pass

    atexit.register(readline.write_history_file, histfile)

Python が 対話モード で実行される時、このコードは実際には自動的に実行されます ( readline の設定 を参照してください)。

次の例では上記と同じ目的を達成できますが、ここでは新規の履歴のみを追加することで、並行して対話セッションがサポートされます:

    import atexit
    import os
    import readline
    histfile = os.path.join(os.path.expanduser("~"), ".python_history")

    try:
        readline.read_history_file(histfile)
        h_len = readline.get_current_history_length()
    except FileNotFoundError:
        open(histfile, 'wb').close()
        h_len = 0

    def save(prev_h_len, histfile):
        new_h_len = readline.get_current_history_length()
        readline.set_history_length(1000)
        readline.append_history_file(new_h_len - prev_h_len, histfile)
    atexit.register(save, h_len, histfile)

次の例では `code.InteractiveConsole` クラスを拡張し、履歴の保存・復旧をサポートします。

    import atexit
    import code
    import os
    import readline

    class HistoryConsole(code.InteractiveConsole):
        def __init__(self, locals=None, filename="<console>",
                     histfile=os.path.expanduser("~/.console-history")):
            code.InteractiveConsole.__init__(self, locals, filename)
            self.init_history(histfile)

        def init_history(self, histfile):
            readline.parse_and_bind("tab: complete")
            if hasattr(readline, "read_history_file"):
                try:
                    readline.read_history_file(histfile)
                except FileNotFoundError:
                    pass
                atexit.register(self.save_history, histfile)

        def save_history(self, histfile):
            readline.set_history_length(1000)
            readline.write_history_file(histfile)