Python: basic python programming with pyTree interface


This tutorial shows some basics using Cassiopee pyTree API. The pyTree is a mapping of CGNS standard.


We need first to provide access to the module functions (here Converter and Generator):
import Converter.PyTree as C
import Generator.PyTree as G

Create a structured array corresponding to a regular Cartesian grid:
a = G.cart( (0,0,0), (1,1,1), (10,11,12) )

a is then a zone node. Each node of a pyTree is a python list of of type: ['Name', n, [], 'NodeType_t'] where 'Name' is the name if the node, n is a numpy containing the data, [] is a list of sons of this node, 'NodeType_t' describes the type of node.
You can of course manipulate the nodes with direct access:
print a[2][0]
But, it is easier to use the Internal module.

Print to screen the zone node:
Internal.printTree(a)

You can always access the numpy storing data, for example 'CoordinateX' by:
n = Internal.getNodeFromName(a, 'CoordinateX')[1]

Convert the previous array as an HEXA unstructured array:
b = C.convertArray2Hexa(a)
Cassiopee functions return a copy of zone a. It is possible to modify directly a without copy (the so called in-place treatment). Simply call the function preceded by a _:
C._convertArray2Hexa(a)
a is then modified.

[Download python script].
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