Pandas API¶

The purpose of this notebook is to provide a demonstration of the capabilities of the pandas like API for PyKX Table objects.

To follow along please download this notebook using the following 'link.'

This demonstration will outline the following

1. Metadata properites
2. Indexing operations

In [1]:

import os
# While this feature is in beta it must be explicitely enabled with this environment variable
# or by adding the `--pandas-api` flag to the QARGS environment variable
os.environ['PYKX_ENABLE_PANDAS_API'] = 'true'
import pykx as kx

import os # While this feature is in beta it must be explicitely enabled with this environment variable # or by adding the `--pandas-api` flag to the QARGS environment variable os.environ['PYKX_ENABLE_PANDAS_API'] = 'true' import pykx as kx

Metadata¶

In [2]:

kx.q('N: 1000')
tab = kx.q('([] x: til N; y: N?`AAPL`GOOG`MSFT; z: N?500f; w: N?1000; v: N?(0N 0 50 100 200 250))')
tab

kx.q('N: 1000') tab = kx.q('([] x: til N; y: N?`AAPL`GOOG`MSFT; z: N?500f; w: N?1000; v: N?(0N 0 50 100 200 250))') tab

Out[2]:

pykx.Table(pykx.q('
x  y    z        w   v  
------------------------
0  AAPL 280.0322 868 200
1  MSFT 48.24615 18     
2  AAPL 66.99184 301 50 
3  MSFT 435.7574 951 0  
4  AAPL 385.586  365 50 
5  AAPL 325.6626 386 0  
6  GOOG 68.13659 844 50 
7  AAPL 399.9134 972 100
8  AAPL 310.2315 457 50 
9  GOOG 486.8679 475 250
10 AAPL 483.0258 28  200
11 MSFT 210.9703 387 250
12 AAPL 49.11884 205 0  
13 GOOG 463.9106 628    
14 MSFT 144.0166 848 250
15 AAPL 258.0005 832 50 
16 MSFT 420.7807 117 200
17 GOOG 327.0546 914 250
18 MSFT 421.2875 470 0  
19 MSFT 481.383  446 50 
..
'))

Table.columns¶

Get the name of each column in the table

In [3]:

tab.columns

tab.columns

Out[3]:

['x', 'y', 'z', 'w', 'v']

Table.dtypes¶

Get the pandas dtype of each column

In [4]:

tab.dtypes

tab.dtypes

Out[4]:

x      int64
y     object
z    float64
w      int64
v      int64
dtype: object

Table.empty¶

Returns True if the table is empty otherwise returns False.

In [5]:

tab.empty

tab.empty

Out[5]:

False

Table.ndim¶

Get the nuber of columns within the table.

In [6]:

tab.ndim

tab.ndim

Out[6]:

5

Table.shape¶

Get the shape of the table as a tuple (number of rows, number of columns).

In [7]:

tab.shape

tab.shape

Out[7]:

(1000, 5)

Table.size¶

Get the number of values in the table (rows * cols).

In [8]:

tab.size

tab.size

Out[8]:

5000

Indexing¶

In [9]:

# The examples in this section will use this example table filled with random data
kx.q('N: 1000')
tab = kx.q('([] x: til N; y: N?`AAPL`GOOG`MSFT; z: N?500f; w: N?1000; v: N?(0N 0 50 100 200 250))')
tab

# The examples in this section will use this example table filled with random data kx.q('N: 1000') tab = kx.q('([] x: til N; y: N?`AAPL`GOOG`MSFT; z: N?500f; w: N?1000; v: N?(0N 0 50 100 200 250))') tab

Out[9]:

pykx.Table(pykx.q('
x  y    z        w   v  
------------------------
0  AAPL 60.54614 184    
1  GOOG 292.5522 299 100
2  GOOG 283.0627 411 250
3  MSFT 42.38194 713 0  
4  MSFT 453.4634 69  100
5  MSFT 12.28187 127 50 
6  MSFT 76.00103 898 200
7  AAPL 17.802   822 0  
8  AAPL 68.05945 197 0  
9  AAPL 405.7366 56  0  
10 MSFT 15.16717 964 50 
11 GOOG 164.3905 826    
12 MSFT 81.26465 593 250
13 MSFT 218.853  332 200
14 MSFT 181.2571 502 50 
15 MSFT 311.1167 705 100
16 GOOG 81.45016 110    
17 AAPL 70.85145 722 50 
18 AAPL 172.3351 410 100
19 AAPL 9.906452 757 200
..
'))

Table.head()¶

Table.head(n=5)

Get the first n rows from a table.

Parameters:

Name	Type	Description	Default
n	int	The number of rows to return.	5

Returns:

Type	Description
Table	The first n rows of the table.

Examples:

Return the first 5 rows of the table.

In [10]:

tab.head()

tab.head()

Out[10]:

pykx.Table(pykx.q('
x y    z        w   v  
-----------------------
0 AAPL 60.54614 184    
1 GOOG 292.5522 299 100
2 GOOG 283.0627 411 250
3 MSFT 42.38194 713 0  
4 MSFT 453.4634 69  100
'))

Return the first 10 rows of the table.

In [11]:

tab.head(10)

tab.head(10)

Out[11]:

pykx.Table(pykx.q('
x y    z        w   v  
-----------------------
0 AAPL 60.54614 184    
1 GOOG 292.5522 299 100
2 GOOG 283.0627 411 250
3 MSFT 42.38194 713 0  
4 MSFT 453.4634 69  100
5 MSFT 12.28187 127 50 
6 MSFT 76.00103 898 200
7 AAPL 17.802   822 0  
8 AAPL 68.05945 197 0  
9 AAPL 405.7366 56  0  
'))

Table.tail()¶

Table.tail(n=5)

Get the last n rows from a table.

Parameters:

Name	Type	Description	Default
n	int	The number of rows to return.	5

Returns:

Type	Description
Table	The last n rows of the table.

Examples:

Return the last 5 rows of the table.

In [12]:

tab.tail()

tab.tail()

Out[12]:

pykx.Table(pykx.q('
x   y    z        w   v 
------------------------
995 AAPL 54.79148 295   
996 AAPL 448.0876 779   
997 GOOG 173.26   896 0 
998 GOOG 350.8906 200 50
999 MSFT 409.2486 807   
'))

Return the last 10 rows of the table.

In [13]:

tab.tail(10)

tab.tail(10)

Out[13]:

pykx.Table(pykx.q('
x   y    z        w   v  
-------------------------
990 GOOG 407.4229 546 100
991 AAPL 18.6764  228 50 
992 AAPL 408.8369 665 200
993 AAPL 282.1039 166    
994 GOOG 69.54563 273 200
995 AAPL 54.79148 295    
996 AAPL 448.0876 779    
997 GOOG 173.26   896 0  
998 GOOG 350.8906 200 50 
999 MSFT 409.2486 807    
'))

Table.get()¶

Table.get(key, default=None)

Get a column or columns from a table by key, if the key does not exist return the default value.

Parameters:

Name	Type	Description	Default
key	Union[str, list[str]]	The column name or list of names to get from the table.	required
default	int	The default value if the key is not found.	None

Returns:

Type	Description
Union[Table, Any]	A table contatining only the columns requested or the default value.

Examples:

Get the y column from the table.

In [14]:

tab.get('y')

tab.get('y')

Out[14]:

pykx.Table(pykx.q('
y   
----
AAPL
GOOG
GOOG
MSFT
MSFT
MSFT
MSFT
AAPL
AAPL
AAPL
MSFT
GOOG
MSFT
MSFT
MSFT
MSFT
GOOG
AAPL
AAPL
AAPL
..
'))

Get the y and z columns from the table.

In [15]:

tab.get(['y', 'z'])

tab.get(['y', 'z'])

Out[15]:

pykx.Table(pykx.q('
y    z       
-------------
AAPL 60.54614
GOOG 292.5522
GOOG 283.0627
MSFT 42.38194
MSFT 453.4634
MSFT 12.28187
MSFT 76.00103
AAPL 17.802  
AAPL 68.05945
AAPL 405.7366
MSFT 15.16717
GOOG 164.3905
MSFT 81.26465
MSFT 218.853 
MSFT 181.2571
MSFT 311.1167
GOOG 81.45016
AAPL 70.85145
AAPL 172.3351
AAPL 9.906452
..
'))

Attempt to get the q column from the table and recieve none as that column does not exist.

In [16]:

print(tab.get('q'))

print(tab.get('q'))

None

Attempt to get the q column from the table and recieve the default value not found as that column does not exist.

In [17]:

tab.get('q', 'not found')

tab.get('q', 'not found')

Out[17]:

'not found'

Table.at[]¶

Table.at[row, col]

Access a single value for a row / column pair.

Similar to loc[], in that both provide label-based lookups. Use at if you only need to get or set a single value.

The at property can be used for both assignment and retrieval of values at a given row and column.

Examples:

Get the value of the z column in the 997th row.

In [18]:

tab.at[997, 'z']

tab.at[997, 'z']

Out[18]:

pykx.FloatAtom(pykx.q('173.26'))

Reassign the value of the z column in the 997th row to 3.14159.

In [19]:

tab.at[997, 'z'] = 3.14159
tab.at[997, 'z']

tab.at[997, 'z'] = 3.14159 tab.at[997, 'z']

Out[19]:

pykx.FloatAtom(pykx.q('3.14159'))

Table.loc[]¶

Table.loc[:, :]

Access a group of rows and columns by label or by BooleanVector.

loc is a label based form of indexing, but may also be used with a boolean array.

Allowed inputs are:

• A single label, e.g. 5 or 'a', (note that 5 is interpreted as a label of the index, and never as an integer position along the index)
• A list or array of labels, e.g. ['a', 'b', 'c']
• A slice object with labels, e.g. 'a':'f'
  • Warning contrary to usual python slices, both the start and the stop are included
• A BooleanVector of the same length as the axis being sliced
• An alignable BooleanVector. The index of the key will be aligned before masking
• An alignable Index. The Index of the returned selection will be the input
• A callable function with one argument (the calling Table like object) and that returns valid output for indexing (e.g. one of the above)

Note: When the Pandas API is enabled, using [] to index into a table will use Table.loc[]

Returns:

Type	Description
Table	A table contatining only the columns / rows requested.

Examples:

Get every row in the y column.

In [20]:

tab[:, 'y']

tab[:, 'y']

Out[20]:

pykx.Table(pykx.q('
y   
----
AAPL
GOOG
GOOG
MSFT
MSFT
MSFT
MSFT
AAPL
AAPL
AAPL
MSFT
GOOG
MSFT
MSFT
MSFT
MSFT
GOOG
AAPL
AAPL
AAPL
..
'))

Get all rows of the table where the value in the z column is greater than 250.0

In [21]:

tab[tab['z'] > 250.0]

tab[tab['z'] > 250.0]

Out[21]:

pykx.Table(pykx.q('
x  y    z        w   v  
------------------------
1  GOOG 292.5522 299 100
2  GOOG 283.0627 411 250
4  MSFT 453.4634 69  100
9  AAPL 405.7366 56  0  
15 MSFT 311.1167 705 100
22 MSFT 325.2313 425 100
23 GOOG 389.6867 143 200
26 MSFT 374.9333 225    
27 AAPL 351.9635 242 200
28 AAPL 292.2184 153 50 
30 MSFT 445.9395 900 100
31 AAPL 406.9874 495 250
32 GOOG 484.709  127    
37 MSFT 354.8972 965    
39 MSFT 323.4569 825 100
40 GOOG 446.6471 161 0  
44 GOOG 465.8163 447 0  
47 AAPL 251.128  608 250
49 MSFT 315.3486 997    
51 GOOG 379.302  16  0  
..
'))

Replace all null values in the column v with the value -100.

In [22]:

tab.loc[tab['v'] == kx.q('0N'), 'v'] = -100
tab

tab.loc[tab['v'] == kx.q('0N'), 'v'] = -100 tab

Out[22]:

pykx.Table(pykx.q('
x  y    z        w   v   
-------------------------
0  AAPL 60.54614 184 -100
1  GOOG 292.5522 299 100 
2  GOOG 283.0627 411 250 
3  MSFT 42.38194 713 0   
4  MSFT 453.4634 69  100 
5  MSFT 12.28187 127 50  
6  MSFT 76.00103 898 200 
7  AAPL 17.802   822 0   
8  AAPL 68.05945 197 0   
9  AAPL 405.7366 56  0   
10 MSFT 15.16717 964 50  
11 GOOG 164.3905 826 -100
12 MSFT 81.26465 593 250 
13 MSFT 218.853  332 200 
14 MSFT 181.2571 502 50  
15 MSFT 311.1167 705 100 
16 GOOG 81.45016 110 -100
17 AAPL 70.85145 722 50  
18 AAPL 172.3351 410 100 
19 AAPL 9.906452 757 200 
..
'))

Replace all locations in column v where the value is -100 with a null.

In [23]:

tab[tab['v'] == -100, 'v'] = kx.q('0N')
tab

tab[tab['v'] == -100, 'v'] = kx.q('0N') tab

Out[23]:

pykx.Table(pykx.q('
x  y    z        w   v  
------------------------
0  AAPL 60.54614 184    
1  GOOG 292.5522 299 100
2  GOOG 283.0627 411 250
3  MSFT 42.38194 713 0  
4  MSFT 453.4634 69  100
5  MSFT 12.28187 127 50 
6  MSFT 76.00103 898 200
7  AAPL 17.802   822 0  
8  AAPL 68.05945 197 0  
9  AAPL 405.7366 56  0  
10 MSFT 15.16717 964 50 
11 GOOG 164.3905 826    
12 MSFT 81.26465 593 250
13 MSFT 218.853  332 200
14 MSFT 181.2571 502 50 
15 MSFT 311.1167 705 100
16 GOOG 81.45016 110    
17 AAPL 70.85145 722 50 
18 AAPL 172.3351 410 100
19 AAPL 9.906452 757 200
..
'))

Table.iloc[]¶

Table.iloc[:, :]

Purely integer-location based indexing for selection by position.

iloc is primarily integer position based (from 0 to length-1 of the axis), but may also be used with a BooleanVector.

Allowed inputs are:

• An integer, e.g. 5.
• A list or array of integers, e.g. [4, 3, 0].
• A slice object with ints, e.g. 1:7.
• A BooleanVector.
• A callable function with one argument (the calling Series or DataFrame) and that returns valid output for indexing (one of the above). This is useful in method chains, when you don’t have a reference to the calling object, but would like to base your selection on some value.
• A tuple of row and column indexes. The tuple elements consist of one of the above inputs, e.g. (0, 1).

Returns:

Type	Description
Table	A table contatining only the columns / rows requested.

Examples:

Get the second row from a table.

In [24]:

tab.iloc[1]

tab.iloc[1]

Out[24]:

pykx.Table(pykx.q('
x y    z        w   v  
-----------------------
1 GOOG 292.5522 299 100
'))

Get the first 5 rows from a table.

In [25]:

tab.iloc[:5]

tab.iloc[:5]

Out[25]:

pykx.Table(pykx.q('
x y    z        w   v  
-----------------------
0 AAPL 60.54614 184    
1 GOOG 292.5522 299 100
2 GOOG 283.0627 411 250
3 MSFT 42.38194 713 0  
4 MSFT 453.4634 69  100
'))

Get all rows of the table where the y column is equal to AAPL.

In [26]:

tab.iloc[tab['y'] == 'AAPL']

tab.iloc[tab['y'] == 'AAPL']

Out[26]:

pykx.Table(pykx.q('
x  y    z        w   v  
------------------------
0  AAPL 60.54614 184    
7  AAPL 17.802   822 0  
8  AAPL 68.05945 197 0  
9  AAPL 405.7366 56  0  
17 AAPL 70.85145 722 50 
18 AAPL 172.3351 410 100
19 AAPL 9.906452 757 200
20 AAPL 199.5309 790    
25 AAPL 27.35117 145 0  
27 AAPL 351.9635 242 200
28 AAPL 292.2184 153 50 
31 AAPL 406.9874 495 250
35 AAPL 199.1284 252 200
38 AAPL 192.8447 604    
45 AAPL 241.7971 919 50 
46 AAPL 25.79979 131 50 
47 AAPL 251.128  608 250
54 AAPL 374.937  986    
57 AAPL 401.5671 996    
58 AAPL 181.9741 768    
..
'))

Get all rows of the table where the y column is equal to AAPL, and only return the y, z and w columns.

In [27]:

tab.iloc[tab['y'] == 'AAPL', ['y', 'z', 'w']]

tab.iloc[tab['y'] == 'AAPL', ['y', 'z', 'w']]

Out[27]:

pykx.Table(pykx.q('
y    z        w  
-----------------
AAPL 60.54614 184
AAPL 17.802   822
AAPL 68.05945 197
AAPL 405.7366 56 
AAPL 70.85145 722
AAPL 172.3351 410
AAPL 9.906452 757
AAPL 199.5309 790
AAPL 27.35117 145
AAPL 351.9635 242
AAPL 292.2184 153
AAPL 406.9874 495
AAPL 199.1284 252
AAPL 192.8447 604
AAPL 241.7971 919
AAPL 25.79979 131
AAPL 251.128  608
AAPL 374.937  986
AAPL 401.5671 996
AAPL 181.9741 768
..
'))

Replace all null values in the column v with the value -100.

In [28]:

tab.iloc[tab['v'] == kx.q('0N'), 'v'] = -100
tab

tab.iloc[tab['v'] == kx.q('0N'), 'v'] = -100 tab

Out[28]:

pykx.Table(pykx.q('
x  y    z        w   v   
-------------------------
0  AAPL 60.54614 184 -100
1  GOOG 292.5522 299 100 
2  GOOG 283.0627 411 250 
3  MSFT 42.38194 713 0   
4  MSFT 453.4634 69  100 
5  MSFT 12.28187 127 50  
6  MSFT 76.00103 898 200 
7  AAPL 17.802   822 0   
8  AAPL 68.05945 197 0   
9  AAPL 405.7366 56  0   
10 MSFT 15.16717 964 50  
11 GOOG 164.3905 826 -100
12 MSFT 81.26465 593 250 
13 MSFT 218.853  332 200 
14 MSFT 181.2571 502 50  
15 MSFT 311.1167 705 100 
16 GOOG 81.45016 110 -100
17 AAPL 70.85145 722 50  
18 AAPL 172.3351 410 100 
19 AAPL 9.906452 757 200 
..
'))

Table.pop()¶

Table.pop(item)

Remove a column or columns from a table by column name and return the column after it has been removed.

Parameters:

Name	Type	Description	Default
item	Union[str, list[str]]	The column name or list of names to pop from the table.	required

Returns:

Type	Description
Table	A table contatining only the columns removed from the input table.

Examples:

Remove the v column from the table and return it.

In [29]:

print(f'{tab.head()}\n\n')
print('Pop the `v` column out of the table')
print(f'{tab.pop("v").head()}\n\n')
print('Updated Table')
print(tab.head())

print(f'{tab.head()}\n\n') print('Pop the `v` column out of the table') print(f'{tab.pop("v").head()}\n\n') print('Updated Table') print(tab.head())

x y    z        w   v   
------------------------
0 AAPL 60.54614 184 -100
1 GOOG 292.5522 299 100 
2 GOOG 283.0627 411 250 
3 MSFT 42.38194 713 0   
4 MSFT 453.4634 69  100 


Pop the `v` column out of the table
v   
----
-100
100 
250 
0   
100 


Updated Table
x y    z        w  
-------------------
0 AAPL 60.54614 184
1 GOOG 292.5522 299
2 GOOG 283.0627 411
3 MSFT 42.38194 713
4 MSFT 453.4634 69 

Remove the z and w columns from the table and return them.

In [30]:

print(f'{tab.head()}\n\n')
print('Pop the `z` and `w` columns out of the table')
print(f'{tab.pop(["z", "w"]).head()}\n\n')
print('Updated Table')
print(tab.head())

print(f'{tab.head()}\n\n') print('Pop the `z` and `w` columns out of the table') print(f'{tab.pop(["z", "w"]).head()}\n\n') print('Updated Table') print(tab.head())

x y    z        w  
-------------------
0 AAPL 60.54614 184
1 GOOG 292.5522 299
2 GOOG 283.0627 411
3 MSFT 42.38194 713
4 MSFT 453.4634 69 


Pop the `z` and `w` columns out of the table
z        w  
------------
60.54614 184
292.5522 299
283.0627 411
42.38194 713
453.4634 69 


Updated Table
x y   
------
0 AAPL
1 GOOG
2 GOOG
3 MSFT
4 MSFT