Numpy append not adding row to Numpy array

Question

I have a method where it checks if we are at row 0.

If yes: it creates the Numpy array as that row. If no: it appends the row to the Numpy array

def printStatement(row):  
    global newData
    if(count == 0):
        newData = np.array(row)

    else:
        print("Made it to second row")
        np.append(newData, row)

It does confirm that it made it to the else statement. But newData does not grow past the first row.

Is there something I need to specify when creating the array? All rows are the same shape.

***2D Array (Added for search engine)

Have you tried np.array([row, row, row,...])?

hpaulj
– hpaulj

2021-03-29 05:58:00 +00:00
Commented Mar 29, 2021 at 5:58 — hpaulj
– hpaulj, Commented Mar 29, 2021 at 5:58
There are 23k+ rows.

llamaCaraDara
– llamaCaraDara

2021-03-29 12:59:46 +00:00
Commented Mar 29, 2021 at 12:59 — llamaCaraDara
– llamaCaraDara, Commented Mar 29, 2021 at 12:59

ev-br · Accepted Answer · 2021-03-29 05:16:55Z

1

You're not storing the result, assign it to something. E.g. newData = no.append(newData, row)

Quoting https://numpy.org/doc/stable/reference/generated/numpy.append.html:

A copy of arr with values appended to axis. Note that append does not occur in-place: a new array is allocated and filled.

And by the way, prefer avoiding np.append unless really necessary.

answered Mar 29, 2021 at 5:16

ev-br

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4 Comments

llamaCaraDara Over a year ago

What do i use instead?

ev-br Over a year ago

prefer a list, convert to an array once

llamaCaraDara Over a year ago

I'm trying to understand what you mean. Can you elaborate?

ev-br Over a year ago

All I'm saying is collect the rows in a list, then convert to array in one go.

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