70 lines of NumPy
This code solves the MuMag standard problem #4 in less than 70 lines of pure Python without counting empty lines and comments :). The code makes largely use of the NumPy library and computes the exchange field by finite differences and the demagnetization field with a fast convolution algorithm. Since the magnetization in finite-difference micromagnetics is represented by a multi-dimensional array and the NumPy library features a rich interface for this data structure, the presented code is a good starting point for the development of novel algorithms.
A detailed description of the code can be found here: http://arxiv.org/abs/1411.7188