"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。

Availability: not Android, not iOS, not WASI.

This module is not supported on mobile platforms or WebAssembly
platforms.

注釈:

  下層の Readline ライブラリー API は GNU readline ではなく "editline"
  ("libedit") ライブラリーで実装される可能性があります。 macOS では
  "readline" モジュールはどのライブラリーが使われているかを実行時に検
  出します。The configuration file for "editline" is different from
  that of GNU readline. If you programmatically load configuration
  strings you can use "backend" to determine which library is being
  used.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.

readline.backend

   The name of the underlying Readline library being used, either
   ""readline"" or ""editline"".

   Added in version 3.13.


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)
