对pandas数据判断是否为NaN值的方法详解

def age_map(x): if x < 26:  return 0 elif x >=26 and x <= 35:  return 1 elif x > 35 and x <= 45:  return 2 elif pd.isnull(x): #判断是否为NaN值，== 和in 都无法判断  return 3 else:  return 4

pd.isnull(x) 

data['age'] = data['birth_year'].map(age_map)