1.set_index
DataFrame可以通過set_index方法,可以設置單索引和複合索引。
DataFrame.set_index(keys, drop=True, append=False, inplace=False, verify_integrity=False)
append添加新索引,drop爲False,inplace爲True時,索引將會還原爲列
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In [307]: data
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Out[307]:
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a b c d
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0 bar one z 1.0
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1 bar two y 2.0
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2 foo one x 3.0
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3 foo two w 4.0
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In [308]: indexed1 = data.set_index('c')
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In [309]: indexed1
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Out[309]:
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a b d
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c
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z bar one 1.0
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y bar two 2.0
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x foo one 3.0
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w foo two 4.0
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In [310]: indexed2 = data.set_index(['a', 'b'])
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In [311]: indexed2
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Out[311]:
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c d
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a b
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bar one z 1.0
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two y 2.0
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foo one x 3.0
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two w 4.0
2.reset_index
reset_index可以還原索引,從新變爲默認的整型索引
DataFrame.reset_index(level=None, drop=False, inplace=False, col_level=0, col_fill=”)
level控制了具體要還原的那個等級的索引
drop爲False則索引列會被還原爲普通列,否則會丟失
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In [318]: data
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Out[318]:
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c d
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a b
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bar one z 1.0
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two y 2.0
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foo one x 3.0
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two w 4.0
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In [319]: data.reset_index()
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Out[319]:
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a b c d
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0 bar one z 1.0
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1 bar two y 2.0
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2 foo one x 3.0
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3 foo two w 4.0