L-Py, an open L-systems framework in Python

L-systems were conceived as a mathematical framework for modeling growth of plants. In this paper, we present L-Py, a simulation software that mixes L-systems construction with the Python high-level modeling language. In addition to this software module, an integrated visual development environment has been developed that facilitates the creation of plant models. In particular, easy to use optimization tools have been integrated. Thanks to Python and its modular approach, this framework makes it possible to integrate a variety of tools defined in different modeling context, in particular tools from the OpenAlea platform. Additionally, it can be integrated as a simple growth simulation module into more complex computational pipelines. The L-Py development environment The central idea of L-systems consists of the rewriting of a string of modules representing the structure of the plant. The rewriting rules (productions) express the creation and changes of state of the plant modules throughout time. Such rules can be expressed using a dedicated programming language (Prusinkiewicz et al., 99) or by incorporating L-system-based language constructs into existing languages, such as C++ (Karwowski and Prusinkiewicz 03) or Java (Kniemeyer and Kurth, 08). In this work, we explore the use of the Python language as support for L-systems. Indeed, Python offers a powerful modeling language with high level structures and constructs. It is interpreted and makes it possible to explore easily and interactively the various complex structures involved in a program. Integrating L-systems in Python – We followed similar methodology than lpfg (Karwowski and Prusinkiewicz, 03). L-systems constructs are integrated into regular python code. In a first part of the L-Py code of a model, modules can optionally be declared possibly with parameter names and global properties using the following syntax.