Ok this is not runtime mel exactly as such, its a code snippet from a maya ascii files. They can not always be translated to runtime coding environment codes, because the slots dont always correspond with attributes that get evaluated. Thus its not really smart to convert them to code directly as such.
.ktv is one attribute you should not manipulate using setAttr, its not so much that you can not its just that it wont really work out for you. In fact if you run that snippet as mel you do get a anim curve node BUT WITH NO KEYFRAMES. So even the mel snippet needs to be translated into mel that can work in a interactive maya! Off course since python is not defined for maya ascii you cant covert the files to python either so if thats your intention then no out of luck.
So your code first need to become workable intentions for maya and it reduces to:
import maya.cmds as cmds
cmds.createNode( "animCurveTL", n="pCube1_translateX")
cmds.setAttr(".tan", 10)
cmds.setAttr(".wgt",0)
cmds.setKeyframe(t=range(1,24))
Tough all but the last line is needed you can skip making the anim curve ans just tell setKeyframe to work on the attribute directly too:
import maya.cmds as cmds
cmds.setKeyframe("pCube1.tx", t=range(1,24))