Blender Python API: Gets materials by creating them or getting them by name.

get_blender_materials.py

import bpy

def get_material(material_name: str) -> bpy.types.Material:
    return bpy.data.materials.get(material_name) or bpy.data.materials.new(name=material_name)

def get_materials(material_names: list) -> list:
    return [get_material(mat_name) for mat_name in material_names]

if __name__ == __main__:
    get_material("TEST_MAT")
    get_materials(["TEST_MAT", "MAT1", "MAT2"])