Hello and welcome,
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I tried your code in a R20 script and it seems to work perfectly fine:
rd = doc.GetActiveRenderData() if rd is None: return fromSlice = rd[c4d.RDATA_FRAMEFROM] toSlice = rd[c4d.RDATA_FRAMETO] fps = doc.GetFps() print(fromSlice.GetFrame(fps)) print(toSlice.GetFrame(fps)What exactly is not working for you? In what context do you execute your code?
best wishes,
Sebastian