optimist

optimist
/-mɪst; -mɪst/ n
person who is always hopeful and expects the best in all things 乐观的人; 乐观主义者
    He's such an optimist that he's sure he'll soon find a job. 他很乐观, 认为自己一定很快就能找到工作. Cf 参看 pessimist (pessimism).

牛津英汉双解词典