image.png
查看空值的len：
import numpy as np
sales_customer_order_11[sales_customer_order_11['birth_year'].isin([np.NaN])]
数量并不多，直接筛选掉即可：
sales_customer_order_11['birth_year'] = sales_customer_order_11[~sales_customer_order_11['birth_year'].\
isin([np.NaN])]['birth_year'].astype('int')
