Design by contract for python']python

The idea of design by contract (DEC), realized in the statically typed object-oriented programming language Eiffel, can be viewed as a systematic approach to specifying and implementing object-oriented software systems. We believe that a statically typed programming language is not suitable in the analysis and design phase of a prototyping-oriented software life cycle. For this purpose, dynamically typed interpreted programming languages art: better suited. Unfortunately, dynamically typed programming languages usually do not support the concept of DBC. Therefore we integrated DEC into the programming language Python by using a metaprogramming approach, i.e., without changing the language or the run-time system. We adopted the DEC concept by adding mechanisms for dynamic type checking for method parameters and instance variables. The proposed combination of a more formal approach with a slim programming language provides a good basis for elicitation and documentation tasks in the analysis and design phase, especially in cases of a prototyping-oriented software development approach. Although the approach presented provides basic tool support for the analysis and design phase, further tool support, especially for browsing assertions, is desirable.