bpython

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.
• Auto-indentation.
• Python 3 support.