How can I trigger a callback whenever a keyframe is set?

I needed a way to know whenever a keyframe was set in Maya: There didn't seem to be a way to do this via a scriptJob, but the API to the rescue.

The below callback will print the names of the animCurve nodes modified whenever a keyframe is set.
However, even though the incoming argument to the editedCurves parameter is an MObjectArray, it only has a single item (based on testing), meaning if you have 10 nodes selected, this code will be executed 10 separate times using addAnimCurveEditedCallback:

import maya.OpenMaya as om
import maya.OpenMayaAnim as oma

def animFunc(editedCurves, *args):
    """
    editedCurves : MObjectArray
    """
    for i in range(editedCurves.length()):
        mFnDependNode = om.MFnDependencyNode(editedCurves[i])
        nodeName = mFnDependNode.name()
        print i,nodeName

cid = oma.MAnimMessage.addAnimCurveEditedCallback(animFunc)

# Delete the callback later:
om.MMessage.removeCallback(cid)

---

If you instead want a callback that iterates over all the channels keyed at once, you can use addAnimKeyframeEditedCallback:

import maya.OpenMaya as om
import maya.OpenMayaAnim as oma

def animFunc(editedKeys, *args):
    """
    editedKeys : MObjectArray
    """
    for i in range(editedKeys.length()):
        mFnKeyframeDelta  = oma.MFnKeyframeDelta(editedKeys[i])
        paramCurve = mFnKeyframeDelta.paramCurve()
        mFnDependNode = om.MFnDependencyNode(paramCurve)
        nodeName = mFnDependNode.name()
        print i,nodeName

cid = oma.MAnimMessage.addAnimKeyframeEditedCallback(animFunc)

Delete the callback later

om.MMessage.removeCallback(cid)