如何使用pandas框架下最长的字符串减少数据？

Question

如何使用pandas框架下最长的字符串减少数据？我尝试了以下代码,但得到了ValueError: invalid number of arguments.

def f1(s):
    return max(s, key=len)

data.groupby('id').agg({'name':(lambda s: f1(s)) })

防爆.输入

id name
GB "United Kingdom"
GB England
US "United States"
US America

输出:

id name
GB "United Kingdom"
US "United States"

Answer 1

代码应该工作.顺便说一句,你不需要换f1另一个lambda.只是通过f1.(它们具有完全相同的参数签名)

>>> import pandas as pd
>>>
>>> def f1(s):
...     return max(s, key=len)
...
>>> data = pd.DataFrame([
...     {'id': 'GB', 'name': '"United Kingdom"'},
...     {'id': 'GB', 'name': 'England'},
...     {'id': 'US', 'name': '"United States"'},
...     {'id': 'US', 'name': 'America'},
...
... ])
>>> data.groupby('id').agg({'name': f1})
                name
id
GB  "United Kingdom"
US   "United States"