first implementation

festim/exports/vtx.py

@@ -0,0 +1,40 @@
+from dolfinx.io import VTXWriter
+import mpi4py
+
+class VTXExport:
+    """Export functions to VTX file
+
+    Args:
+        filename (str): the name of the output file
+
+    Attributes:
+        filename (str): the name of the output file
+        writer (dolfinx.io.VTXWriter): the VTX writer
+    
+    Usage:
+        >>> u = dolfinx.fem.Function(V)
+        >>> my_export = festim.VTXExport("my_export.bp")
+        >>> my_export.define_writer(mesh.comm, [u])
+        >>> for t in range(10):
+        ...    u.interpolate(lambda x: t * (x[0] ** 2 + x[1] ** 2 + x[2] ** 2))
+        ...    my_export.write(t)
+    """
+    def __init__(self, filename: str) -> None:
+        self.filename = filename
+
+    def define_writer(self, comm: mpi4py.MPI.Intracomm, functions: list) -> None:
+        """Define the writer
+
+        Args:
+            comm (mpi4py.MPI.Intracomm): the MPI communicator
+            functions (list): the list of functions to export
+        """
+        self.writer = VTXWriter(comm, self.filename, functions, "BP4")
+
+    def write(self, t:float):
+        """Write functions to VTX file
+
+        Args:
+            t (float): the time of export
+        """
+        self.writer.write(t)