python中pandas.DataFrame的简单操作方法（创建、索引、增添与删除）

In [1]: import pandas as pd
In [3]: aa={'one':[1,2,3],'two':[2,3,4],'three':[3,4,5]}
In [4]: bb=pd.DataFrame(aa)
In [5]: bb
Out[5]: 
 one three two
0 1 3 2
1 2 4 3
2 3 5 4`

bb=pd.DataFrame(aa,index=['first','second','third'])
bb
Out[7]: 
 one three two
first 1 3 2
second 2 4 3
third 3 5 4

import numpy as np
In [9]: del aa
In [10]: aa=np.array([[1,2,3],[4,5,6],[7,8,9]])
In [11]: aa
Out[11]: 
array([[1, 2, 3],
 [4, 5, 6],
 [7, 8, 9]])
In [12]: bb=pd.DataFrame(aa)
In [13]: bb
Out[13]: 
 0 1 2
0 1 2 3
1 4 5 6
2 7 8 9

bb=pd.DataFrame(aa,index=[22,33,44],columns=['one','two','three'])
In [15]: bb
Out[15]: 
 one two three
22 1 2 3
33 4 5 6
44 7 8 9

bb=pd.DataFrame(aa,index=[22,33,44],columns=['one','two','three'])
bb
Out[15]: 
 one two three
22 1 2 3
33 4 5 6
44 7 8 9
cc=bb[['one','three']].copy()
Cc
Out[17]: 
 one three
22 1 3
33 4 6
44 7 9

cc['three'][22]=5
bb
Out[19]: 
 one two three
22 1 2 3
33 4 5 6
44 7 8 9

cc
Out[20]: 
 one three
22 1 5
33 4 6
44 7 9

bb['one']
Out[21]: 
22 1
33 4
44 7
Name: one, dtype: int32

bb[['one','three']]
Out[29]: 
 one three
22 1 3
33 4 6
44 7 9

bb[1:3]
Out[27]: 
 one two three
33 4 5 6
44 7 8 9
bb[:1]
Out[28]: 
 one two three
22 1 2 3

bb.loc[[22,33]][['one','three']]
Out[30]: 
 one three
22 1 3
33 4 6

bb.loc[[22,33]][['one','three']]=[[2,2],[3,6]]
In [32]: bb
Out[32]: 
 one two three
22 1 2 3
33 4 5 6
44 7 8 9

bb[['one','three']][:2]
Out[33]: 
 one three
22 1 3
33 4 6

In [34]: bb[['one','three']][:2]=[[2,2],[2,2]]
-c:1: SettingWithCopyWarning: A value is trying to be set on a copy of a slice from a DataFrame.
Try using .loc[row_index,col_indexer] = value instead
F:\Anaconda\lib\site-packages\pandas\core\frame.py:1999: SettingWithCopyWarning: A value is trying to be set on a copy of a slice from a DataFrame
 return self._setitem_slice(indexer, value)

bb.iloc[2:3,2:3]
Out[36]: 
 three
44 9

bb.iloc[1:3,1:3]
Out[37]: 
 two three
33 5 6
44 8 9
bb.iloc[0,0]
Out[38]: 1

bb.iloc[0:4,0:2]=[[9,9],[9,9],[9,9]]
In [45]: bb
Out[45]: 
 one two three
22 9 9 3
33 9 9 6
44 9 9 9

bb['new']=[2,3,4]
bb
Out[51]: 
 one two three new
22 9 9 3 2
33 9 9 6 3
44 9 9 9 4
bb[['new','new2']]=[[2,3,4],[5,3,7]]
KeyError: "['new' 'new2'] not in index"

aa={33:[234,44,55],44:[657,77,77],22:[33,55,457]}
In [58]: bb=bb.join(pd.DataFrame(aa.values(),columns=['hi','hello','ok'],index=aa.keys()))
In [59]: bb
Out[59]: 
 one two three new hi hello ok
22 9 9 3 2 33 55 457
33 9 9 6 3 234 44 55
44 9 9 9 4 657 77 77

bb.drop(['new','hi'],axis=1)
Out[60]: 
 one two three hello ok
22 9 9 3 55 457
33 9 9 6 44 55
44 9 9 9 77 77

bb.drop([22,33],axis=0)
Out[61]: 
 one two three new hi hello ok
44 9 9 9 4 657 77 77