CODEWITHSUNDEEP
pythonnumpy
Wikunia
Wikunia

Reputation: 1592

View on numpy array

I have a matrix 

 m = np.zeros((5,5))

and what to have a view on the last row

row = m[-1]

however if I add a column to m:

m = np.c_[m[:,:2],[0,0,1,1,1],m[:,2:]]

and print out row I don't get the new column.

Is there any way to get the change without use the line

row = m[-1]

again?

Upvotes: 1

Views: 189

Answers (1)

Oluwafemi Sule
Oluwafemi Sule

Reputation: 38982

What you want to achieve here isn't currently possible within the bounds of the numpy library. See this answer on numpy arrays occupying a contiguous block of memory.

You can use the rx library to get around this by making a subject of the last row.

import numpy as np
from rx import Observable, Observer
from rx.subjects import Subject

m = np.zeros((5,5))

m_stream = Subject()
last_row_stream = Subject()
last_row = None

def update_last(v):
    global last_row
    last_row = v

last_row_stream.subscribe(on_next=update_last)
last_row_stream.on_next(m[-1])

print(last_row)

m_stream.map(
    lambda v: np.insert(v, 2, [0, 0, 1, 1, 1], axis=1)
).subscribe(lambda v: last_row_stream.on_next(v[-1]))

m_stream.on_next(m)


print(last_row)

Upvotes: 1

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