bpython is a fancy interface to the Python interpreter for Unix-like operating systems (I hear it works fine on OS X). It is released under the MIT License. It has the following features:
* In-line syntax highlighting.
* Readline-like autocomplete with suggestions displayed as you type.
* Expected parameter list for any Python function.
* "Rewind" function to pop the last line of code from memory and re-evaluate.
* Send the code you've entered off to a pastebin.
* Save the code you've entered to a file.
There are no reported vulnerabilities