Bone parenting without offset using Python?

Question

import bpy

ob = bpy.data.objects
child = ob['cube']
parent = ob['armature']
bone = parent.pose.bones['bone']

child.parent = parent
child.parent_type = 'BONE'
child.parent_bone = bone

I wrote the script above to carry out bone parenting with Python.
The parenting setting works correctly, but at the end, the child object's transformation will have an offset.
How can I achieve bone parenting without offset?

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Additional questions about batFINGER's answers.
I tested the script. But I still get the offset. Did I make a mistake?
I recorded two GIF to clarify the question.
In the case of the parenting using operator, the cube's transform is maintained, but in the case of parenting using script, the cube's transform changed.

Bone parenting using operator

Bone parenting using script

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1. After creating an armature, change the bone transforms in pose mode.
2. Operate bone parenting with cube & bone of armature.
3. The ops method keeps the cube in place, but the script method changes the cube by the bone transform
4. I want to achieve ops result using python script.

Result by ops (Ctrl+P/Bone after select cube and armature)

Result by script

Answer 1

Set basis and parent inverse to identity.

One of the simplest ways to do this is to set both the basis matrix and parent inverse matrix to identity, to ensure all transforms are those inherited directly.

Getting no feedback re what parenting "without offset" is, have included link to https://blender.stackexchange.com/a/112856/15543 which has a number of methods to parent, either keeping current global location, (the operator result in question EDIT) or snapping to the transform of the parent as shown here..

The confusion is over the term offset. Code below puts an object at its parents transform with no "offset" from it, no local transforms.

Parenting, while maintaining the object in place, could be considered as setting the offset from child to parent, before parenting. If turned on relationship lines are a visual rep'n of the parent to child offset.

Code below is same as 'SNAP_IDENTITY'

import bpy
from mathutils import Matrix
ob = bpy.data.objects
child = ob['Cube']
parent = ob['Armature']
bone = parent.pose.bones['Bone']
child.parent = parent
child.parent_type = 'BONE'
child.parent_bone = bone.name
child.matrix_basis = Matrix() 
child.matrix_parent_inverse = Matrix()

Please also notice that the parent bone setting requires the name of the bone, not the bone itself.