peg as

peg (one) as (something)

To believe or consider that one definitely is a certain type of person or thing. I pegged her as a total bore when she first started working here, but since getting to know her, she's actually pretty interesting. I'm disappointed, Jake—I never pegged you as a quitter.
See also: peg

peg someone as something

 and have someone pegged as something
to think of someone in a certain way. Susan pegged the new employee as a lazy worker. I had you pegged as an angry rebel before I got to know you.
See also: peg