Python 查询多个条件的表时出错

我做错了什么

nondrinkers_21 = bootstrap3[bootstrap3['drinks_coffee']==False]['age']=='<21'['height'].mean()

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nondrinkers_21=bootstrap3[bootstrap3['drinks_coffee']==False]['age']='您的括号放错了位置

nondrinkers_21 = (bootstrap3[(bootstrap3['drinks_coffee']==False) & (bootstrap3['age']<21)])['height'].mean()

nondrinkers_21=（bootstrap3[（bootstrap3['drinks_coffee']==False）和（bootstrap3['age']