  Fluid driven fractures propagate in the upper earth crust either naturally or
in response to engineered fluid injections. The quantitative prediction of
their evolution is critical in order to better understand their dynamics as
well as to optimize their creation. We present a Python implementation of an
open-source hydraulic fracture propagation simulator based on the implicit
level set algorithm originally developed by Peirce & Detournay (2008) -- "An
implicit level set method for modeling hydraulically driven fractures". Comp.
Meth. Appl. Mech. Engng, (33-40):2858--2885. This algorithm couples a finite
discretization of the fracture with the use of the near tip asymptotic
solutions of a steadily propagating semi-infinite hydraulic fracture. This
allows to resolve the multi-scale processes governing hydraulic fracture growth
accurately, even with relatively coarse meshes. We present an overview of the
mathematical formulation, the numerical scheme and the details of our
implementation. A series of problems including a radial hydraulic fracture
verification benchmark, the propagation of a height contained hydraulic
fracture, the lateral spreading of a magmatic dyke and the handling of fracture
closure are presented to demonstrate the capabilities, accuracy and robustness
of the implemented algorithm.
