How to get animated properties of layer

hi everyone, I have added animator in a textlayer and then select 'opacity'

the range selector is based on 'characters' or 'words'

so the textlayer's opacity became varying value, and every character's opacity increase by time

the question is, how can I get every character's opacity at specific time by script?

I have tried these codes, only get "100"

text = curLayer.sourceText

alpha = curLayer.property('opacity').valueAtTime(t, true)

Any ideas?

thank you