Adding new records to a numpy structured array

Question

This is a continuation of an earlier learning on numpy arrays.
A structured array is created from the elements of a list - and thereafter populated with values(not shown below).

>>> o = ['x','y','z']
>>> import numpy as np
>>> b = np.zeros((len(o),), dtype=[(i,object) for i in o])
>>> b
array([(0, 0, 0, 0, 0), (0, 0, 0, 0, 0), (0, 0, 0, 0, 0)], 
      dtype=[('x', '|O4'), ('y', '|O4'), ('z', '|O4')])

The populated array looks as below:

    x   y   z   
x   0   1   0   
y   1   0   1,5 
z   0   1,5 0

1.How do we add new vertices to the above?
2.Once the vertices have been added,what is the cleanest process to add the following array to the structured array(NOTE:not all vertices in this array are new):

    d    e      y
d   0   '1,2'   0
e  '1,2' 0     '1'
f   0   '1'     0

The expected output(please bear with me):

    x   y   z   d   e   f
x   0   1   0   0   0   0
y   1   0   1,5 0   1   0
z   0   1,5 0   0   0   0
d   0   0   0   0   1,2 0
e   0   1   0   1,2 0   0
f   0   0   0   0   1   0

score 0 · Answer 1 · answered Jul 02 '13 at 13:54

Seems like a job for python pandas.

>>> import numpy as np
>>> import pandas as pd
>>> data=np.zeros((4,5))
>>> df=pd.DataFrame(data,columns=['x','y','z','a','b'])
>>> df
   x  y  z  a  b
0  0  0  0  0  0
1  0  0  0  0  0
2  0  0  0  0  0
3  0  0  0  0  0
>>> df['c']=0  #Add a new column
>>> df
   x  y  z  a  b  c
0  0  0  0  0  0  0
1  0  0  0  0  0  0
2  0  0  0  0  0  0
3  0  0  0  0  0  0

>>> new_data=pd.DataFrame([['0','1,2','0'],['1,2','0','1'],['0','1','0']],columns=['d','e','y'])
>>> new_data
     d    e  y
0    0  1,2  0
1  1,2    0  1
2    0    1  0

>>> df.merge(new_data,how='outer') #Merge data
    x  y   z   a   b   c    d    e
0   0  0   0   0   0   0  NaN  NaN
1   0  0   0   0   0   0  NaN  NaN
2   0  0   0   0   0   0  NaN  NaN
3   0  0   0   0   0   0  NaN  NaN
4 NaN  0 NaN NaN NaN NaN    0  1,2
5 NaN  0 NaN NaN NaN NaN    0    1
6 NaN  1 NaN NaN NaN NaN  1,2    0

There are many ways to merge the data that you showed, can you please explain in more detail exactly what you would like the ending array to look like?

Adding new records to a numpy structured array

1 Answers1