如何在DataFrame索引某一行

有行索引和列索引

df=DataFrame(np.arange(16).reshape((4,4)),index=['a','b','c','d'],columns=['one','two','three','four'])

df
Out[14]: 
   one  two  three  four
a    0    1      2     3
b    4    5      6     7
c    8    9     10    11
d   12   13     14    15

po=df.loc[['a','b'],:] 

po
Out[16]: 
   one  two  three  four
a    0    1      2     3
b    4    5      6     7

默认的索引

dd=DataFrame(np.arange(81).reshape((9,9)))

dd
Out[20]: 
    0   1   2   3   4   5   6   7   8
0   0   1   2   3   4   5   6   7   8
1   9  10  11  12  13  14  15  16  17
2  18  19  20  21  22  23  24  25  26
3  27  28  29  30  31  32  33  34  35
4  36  37  38  39  40  41  42  43  44
5  45  46  47  48  49  50  51  52  53
6  54  55  56  57  58  59  60  61  62
7  63  64  65  66  67  68  69  70  71
8  72  73  74  75  76  77  78  79  80

pp=dd.loc[[1,5,7],:]

pp
Out[25]: 
    0   1   2   3   4   5   6   7   8
1   9  10  11  12  13  14  15  16  17
5  45  46  47  48  49  50  51  52  53
7  63  64  65  66  67  68  69  70  71