python-pandas的基本用法05

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pandas的基本用法05-索引

    # -*- coding: utf-8 -*-     import numpy as np    from pandas import Series, DataFrame    from numpy.core.defchararray import index    print 'Series的索引，默认数字索引可以工作。'    s = Series(np.arange(4.), index=['a','b','c','d'])    print s[['a','b']]    # a    0    # b    1    # dtype: float64    print s[[0,1,2]]    # a    0    # b    1    # c    2    # dtype: float64    print s[s>1]    # c    2    # d    3    # dtype: float64    print 'Series的数组切片'    print s['a':'c']    # a    0    # b    1    # c    2    # dtype: float64    print 'DataFrame的索引'    df = DataFrame(np.arange(16).reshape(4,4),                   index = ['a', 'b','c','d'],                   columns=[1,2,3,4]                   )    print df    #     1   2   3   4    # a   0   1   2   3    # b   4   5   6   7    # c   8   9  10  11    # d  12  13  14  15    print '打印列'    print df[[1,2]]    #     1   2    # a   0   1    # b   4   5    # c   8   9    # d  12  13    print '打印行'    print df[:2]    #    1  2  3  4    # a  0  1  2  3    # b  4  5  6  7    print df.ix[:2]    #    1  2  3  4    # a  0  1  2  3    # b  4  5  6  7    print '指定索引和列'    print df.ix[['a','b'], [1,2,3]]    #    1  2  3    # a  0  1  2    # b  4  5  6    print df.ix[:'c', :3]    #    1  2   3    # a  0  1   2    # b  4  5   6    # c  8  9  10    print '根据条件选择'    print df>3    #        1      2      3      4    # a  False  False  False  False    # b   True   True   True   True    # c   True   True   True   True    # d   True   True   True   True    print df[[1,2]]>3    #        1      2    # a  False  False    # b   True   True    # c   True   True    # d   True   True    df[df<3]=0    print df    #     1   2   3   4    # a   0   0   0   3    # b   4   5   6   7    # c   8   9  10  11    # d  12  13  14  15    print df.T    #    a  b   c   d    # 1  0  4   8  12    # 2  0  5   9  13    # 3  0  6  10  14    # 4  3  7  11  15
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