| 合并方法 | SQL 方法 |
|---|---|
| left | LEFT OUTER JOIN |
| right | RIGHT OUTER JOIN |
| outer | FULL OUTER JOIN |
| inner | INNER JOIN |
In [45]: result = pd.merge(left, right, how='left', on=['key1', 'key2'])
指定indicator=True ，可以表示具體行的連接方式：
In [60]: df1 = pd.DataFrame({'col1': [0, 1], 'col_left': ['a', 'b']})
In [61]: df2 = pd.DataFrame({'col1': [1, 2, 2], 'col_right': [2, 2, 2]})
In [62]: pd.merge(df1, df2, on='col1', how='outer', indicator=True)
Out[62]:
col1 col_left col_right _merge
0 0 a NaN left_only
1 1 b 2.0 both
2 2 NaN 2.0 right_only
3 2 NaN 2.0 right_only
如果傳入字符串給indicator，會(huì)重命名indicator這一列的名字：
In [63]: pd.merge(df1, df2, on='col1', how='outer', indicator='indicator_column') Out[63]: col1 col_left col_right indicator_column 0 0 a NaN left_only 1 1 b 2.0 both 2 2 NaN 2.0 right_only 3 2 NaN 2.0 right_only
多個(gè)index進(jìn)行合并：
In [112]: leftindex = pd.MultiIndex.from_tuples([('K0', 'X0'), ('K0', 'X1'),
.....: ('K1', 'X2')],
.....: names=['key', 'X'])
.....:
In [113]: left = pd.DataFrame({'A': ['A0', 'A1', 'A2'],
.....: 'B': ['B0', 'B1', 'B2']},
.....: index=leftindex)
.....:
In [114]: rightindex = pd.MultiIndex.from_tuples([('K0', 'Y0'), ('K1', 'Y1'),
.....: ('K2', 'Y2'), ('K2', 'Y3')],
.....: names=['key', 'Y'])
.....:
In [115]: right = pd.DataFrame({'C': ['C0', 'C1', 'C2', 'C3'],
.....: 'D': ['D0', 'D1', 'D2', 'D3']},
.....: index=rightindex)
.....:
In [116]: result = pd.merge(left.reset_index(), right.reset_index(),
.....: on=['key'], how='inner').set_index(['key', 'X', 'Y'])
支持多個(gè)列的合并：
In [117]: left_index = pd.Index(['K0', 'K0', 'K1', 'K2'], name='key1')
In [118]: left = pd.DataFrame({'A': ['A0', 'A1', 'A2', 'A3'],
.....: 'B': ['B0', 'B1', 'B2', 'B3'],
.....: 'key2': ['K0', 'K1', 'K0', 'K1']},
.....: index=left_index)
.....:
In [119]: right_index = pd.Index(['K0', 'K1', 'K2', 'K2'], name='key1')
In [120]: right = pd.DataFrame({'C': ['C0', 'C1', 'C2', 'C3'],
.....: 'D': ['D0', 'D1', 'D2', 'D3'],
.....: 'key2': ['K0', 'K0', 'K0', 'K1']},
.....: index=right_index)
.....:
In [121]: result = left.merge(right, on=['key1', 'key2'])
join將兩個(gè)不同index的DF合并成一個(gè)。可以看做是merge的簡(jiǎn)寫。
In [84]: left = pd.DataFrame({'A': ['A0', 'A1', 'A2'],
....: 'B': ['B0', 'B1', 'B2']},
....: index=['K0', 'K1', 'K2'])
....:
In [85]: right = pd.DataFrame({'C': ['C0', 'C2', 'C3'],
....: 'D': ['D0', 'D2', 'D3']},
....: index=['K0', 'K2', 'K3'])
....:
In [86]: result = left.join(right)
可以指定how來指定連接方式：
In [87]: result = left.join(right, how='outer')
默認(rèn)join是按index來進(jìn)行連接。
還可以按照列來進(jìn)行連接：
In [91]: left = pd.DataFrame({'A': ['A0', 'A1', 'A2', 'A3'],
....: 'B': ['B0', 'B1', 'B2', 'B3'],
....: 'key': ['K0', 'K1', 'K0', 'K1']})
....:
In [92]: right = pd.DataFrame({'C': ['C0', 'C1'],
....: 'D': ['D0', 'D1']},
....: index=['K0', 'K1'])
....:
In [93]: result = left.join(right, on='key')
單個(gè)index和多個(gè)index進(jìn)行join：
In [100]: left = pd.DataFrame({'A': ['A0', 'A1', 'A2'],
.....: 'B': ['B0', 'B1', 'B2']},
.....: index=pd.Index(['K0', 'K1', 'K2'], name='key'))
.....:
In [101]: index = pd.MultiIndex.from_tuples([('K0', 'Y0'), ('K1', 'Y1'),
.....: ('K2', 'Y2'), ('K2', 'Y3')],
.....: names=['key', 'Y'])
.....:
In [102]: right = pd.DataFrame({'C': ['C0', 'C1', 'C2', 'C3'],
.....: 'D': ['D0', 'D1', 'D2', 'D3']},
.....: index=index)
.....:
In [103]: result = left.join(right, how='inner')
列名重復(fù)的情況：
In [122]: left = pd.DataFrame({'k': ['K0', 'K1', 'K2'], 'v': [1, 2, 3]})
In [123]: right = pd.DataFrame({'k': ['K0', 'K0', 'K3'], 'v': [4, 5, 6]})
In [124]: result = pd.merge(left, right, on='k')
可以自定義重復(fù)列名的命名規(guī)則：
In [125]: result = pd.merge(left, right, on='k', suffixes=('_l', '_r'))
有時(shí)候我們需要使用DF2的數(shù)據(jù)來填充DF1的數(shù)據(jù)，這時(shí)候可以使用combine_first：
In [131]: df1 = pd.DataFrame([[np.nan, 3., 5.], [-4.6, np.nan, np.nan], .....: [np.nan, 7., np.nan]]) .....: In [132]: df2 = pd.DataFrame([[-42.6, np.nan, -8.2], [-5., 1.6, 4]], .....: index=[1, 2]) .....:
In [133]: result = df1.combine_first(df2)
到此這篇關(guān)于Pandas實(shí)現(xiàn)Dataframe的合并的文章就介紹到這了,更多相關(guān)Pandas Dataframe合并內(nèi)容請(qǐng)搜索腳本之家以前的文章或繼續(xù)瀏覽下面的相關(guān)文章希望大家以后多多支持腳本之家！
標(biāo)簽：楊凌 迪慶 六盤水 牡丹江 撫州 揚(yáng)州 聊城 南寧
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