pyexpander is a macro processor based on Python. Instead of simple text replacement, it offers evaluation of arbitrary Python expressions and execution of Python code. It features simple syntax definition: all expander commands start with a dollar sign ("$") followed by word characters, parameters, Python code enclosed in brackets, or a combination of these. The full power of the Python programming language can be used, including all operators, functions and modules. Any Python expression can be used to insert text. It also provides a Python library that you can use to develop other macro tools based on pyexpander.