14. Interactive Input Editing and History Substitution
******************************************************

Some versions of the Python interpreter support editing of the current
input line and history substitution, similar to facilities found in
the Korn shell and the GNU Bash shell.  This is implemented using the
GNU Readline library, which supports various styles of editing.  This
library has its own documentation which we won’t duplicate here.


14.1. Tab Completion and History Editing
========================================

Completion of variable and module names is automatically enabled at
interpreter startup so that the "Tab" key invokes the completion
function; it looks at Python statement names, the current local
variables, and the available module names.  For dotted expressions
such as "string.a", it will evaluate the expression up to the final
"'.'" and then suggest completions from the attributes of the
resulting object.  Note that this may execute application-defined code
if an object with a "__getattr__()" method is part of the expression.
The default configuration also saves your history into a file named
".python_history" in your user directory. The history will be
available again during the next interactive interpreter session.


14.2. Alternatives to the Interactive Interpreter
=================================================

This facility is an enormous step forward compared to earlier versions
of the interpreter; however, some wishes are left: It would be nice if
the proper indentation were suggested on continuation lines (the
parser knows if an indent token is required next).  The completion
mechanism might use the interpreter’s symbol table.  A command to
check (or even suggest) matching parentheses, quotes, etc., would also
be useful.

One alternative enhanced interactive interpreter that has been around
for quite some time is IPython, which features tab completion, object
exploration and advanced history management.  It can also be
thoroughly customized and embedded into other applications.  Another
similar enhanced interactive environment is bpython.
