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import pymel.core as pymel
transform1 = pymel.createNode('transform', name='fk_control')
transform2 = pymel.createNode('transform', name='ik_control')
transform3 = pymel.createNode('transform', name='blender')

transform3.addAttr('ikFkSwitch', keyable=True, min=0, max=1)

for node in transform1, transform2:
    node.addAttr('ikFkSwitch', usedAsProxy=True, keyable=True, min=0, max=1)
    transform3.ikFkSwitch.connect(node.ikFkSwitch)