# The Sage Command Line¶

The Sage Read-Eval-Print-Loop (REPL) is based on IPython. In this document, you’ll find how the IPython integration works. You should also be familiar with the documentation for IPython.

For more details about using the Sage command line, see the Sage tutorial.

## Preparsing¶

Sage commands are “preparsed” to valid Python syntax. This allows for example to support the R.<x> = QQ[] syntax.

## Loading and attaching files¶

Sage or Python files can be loaded (similar to Python’s execfile) in a Sage session. Attaching is similar, except that the attached file is reloaded whenever it is changed.

## Pretty Printing¶

In addition to making input nicer, we also modify how results are printed. This again builds on how IPython formats output. Technically, this works using a modified displayhook in Python.