利用pandas dataframe的groupby和agg方法写词频统计代码的时候，遇到的pandas版本迭代造成的原有代码不可使用的情况。
遇到错误
pandas.core.base.SpecificationError: nested renamer is not supported
问题代码块
words_stst
= word_df
.groupby
(by
='segment')['segment'].agg
({'计数':'size'})
words_stst
= words_stst
.reset_index
().sort_values
(by
=['计数'],ascending
=False)
解决方法
words_stst
= word_df
.groupby
('segment').agg
(计数
=pd
.NamedAgg
(column
='segment', aggfunc
='size')).reset_index
().sort_values
(
by
='计数', ascending
=False)
pandas版本迭代的文档链接
https://pandas.pydata.org/pandas-docs/stable/whatsnew/v0.25.0.html
