DataFrame.filter

DataFrame.filter(items=None, like=None, regex=None, axis=None)
根据指定的索引标签取得DataFrame的行或列的子集。
过滤器应用于索引标签，但不会应用于DataFrame中的数据。

Parameters

Example

import pandas as pd
df = pd.DataFrame({'site':['google', 'baidu', 'wiki'],
                    'age':[18, 39, 22],
                    'price': [1.0, 2.0, 3.0],
                    'color': ['red', 'black', None]},index=['first','second','third'])
df.filter(items=['site', 'age'])
-----------------------------------------------
        site    age
first    google    18
second    baidu    39
third    wiki    22

Example

import pandas as pd
df = pd.DataFrame({'site':['google', 'baidu', 'wiki'],
                    'age':[18, 39, 22],
                    'price': [1.0, 2.0, 3.0],
                    'color': ['red', 'black', None]},index=['first','second','third'])
df.filter(items=['first', 'second'], axis=0)
-------------------------------------------------------
        site    age    price    color
first    google    18    1.0        red
second    baidu    39    2.0        black

Example

import pandas as pd
df = pd.DataFrame({'site':['google', 'baidu', 'wiki'],
                    'age':[18, 39, 22],
                    'price': [1.0, 2.0, 3.0],
                    'color': ['red', 'black', None]},index=['first','second','third'])
df.filter(regex='e$', axis=1)
--------------------------------------------------------
        site    age    price
first    google    18    1.0
second    baidu    39    2.0
third    wiki    22    3.0

Example

import pandas as pd
df = pd.DataFrame({'site':['google', 'baidu', 'wiki'],
                    'age':[18, 39, 22],
                    'price': [1.0, 2.0, 3.0],
                    'color': ['red', 'black', None]},index=['first','second','third'])
df.filter(like='on', axis=0)
-------------------------------------------
        site    age    price    color
second    baidu    39    2.0        black

DataFrameGroupBy.filter

DataFrameGroupBy.filter(func, dropna=True, *args, kwargs)**
返回DataFrame的副本，不包括过滤后的元素。
如果组中的元素不满足func指定的布尔标准，则过滤它们。

Parameters

import pandas as pd
df = pd.DataFrame({'site':['google', 'baidu', 'wiki'],
                    'age':[18, 39, 22],
                    'price': [1.0, 2.0, 3.0],
                    'color': ['red', 'black', None]},index=['first','second','third'])
df.groupby('color').filter(lambda x: x['age'].mean() > 30)
---------------------------------------------------------
        site    age    price    color
second    baidu    39    2.0        black