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import pymel.core as pm
# Hotkey to swap two selected animation curves

curves = pm.keyframe(q=True, selected=True, name=True)

if len(curves) == 2:
    swap_a, swap_b = curves[0], curves[1]
    
    pm.copyKey(swap_a)
    
    # snapshot of swap_b before copying over
    pm.bufferCurve(swap_b, overwrite=True)
    
    pm.pasteKey(swap_b, option='replaceCompletely')
    
    # swap temporarily to previous buffer curve on swap_b
    pm.bufferCurve(swap_b, swap=True)
    pm.copyKey(swap_b)
    
    # swap back
    pm.bufferCurve(swap_b, swap=True)    
    pm.pasteKey(swap_a, option='replaceCompletely')  
else:
    pm.warning('[swap_curves] Select 2 curves.')