blender/doc/python_api/examples/bpy.ops.py

"""
Calling Operators
-----------------

Provides python access to calling operators, this includes operators written in
C, Python or Macros.

Only keyword arguments can be used to pass operator properties.

Operators don't have return values as you might expect, instead they return a
set() which is made up of: {'RUNNING_MODAL', 'CANCELLED', 'FINISHED',
'PASS_THROUGH'}.
Common return values are {'FINISHED'} and {'CANCELLED'}.


Calling an operator in the wrong context will raise a RuntimeError,
there is a poll() method to avoid this problem.

Note that the operator ID (bl_idname) in this example is 'mesh.subdivide',
'bpy.ops' is just the access path for python.


Keywords and Positional Arguments
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

For calling operators keywords are used for operator properties and
positional arguments are used to define how the operator is called.

There are 3 optional positional arguments (documented in detail below).

.. code-block:: python

   bpy.ops.test.operator(override_context, execution_context, undo)

* override_context - dict type
* execution_context - string (enum)
* undo - boolean


Each of these arguments is optional, but must be given in the order above.
"""
import bpy

# calling an operator
bpy.ops.mesh.subdivide(number_cuts=3, smoothness=0.5)


# check poll() to avoid exception.
if bpy.ops.object.mode_set.poll():
    bpy.ops.object.mode_set(mode='EDIT')