Unable to return a numpy array from a column of a pandas DataFrame

Question

I have a pandas DataFrame like so:

      Col_A     Col_B
   0.   1         5
   1.   2         6
   2.   3         7
   3.   4         8

I'm trying to do this to pass a and b as variables inside a function I'm defining. For this, a should be a numpy array of the values in column A but I'm not being able to do that.

So far I've tried:

a = np.empty(1); a.fill(df[0])

But it returns:

ValueError: Input object to FillWithScalar is not a scalar

Typical XY problem. Describe your problem and what you try to do, not why your solution is not working. — Erfan
– Erfan, Commented Jul 9, 2019 at 23:15
@Erfan thank you for pointing this out, I didn't realise while I was writing the question. I think I've made it more clear now. My issue is that I'm not being able to return a numpy array from a column of a pandas DataFrame — Nocas
– Nocas, Commented Jul 9, 2019 at 23:23
Take a step back and 1. provide an example dataset (which you already did). 2. Explain what you try to achieve with your data (pass a and b as variables is not what I mean, thats still your solution). 3. Add an expected output based on your example dataset. — Erfan
– Erfan, Commented Jul 9, 2019 at 23:31
df['A'].to_numpy() or df['A'].values should return column as a 1d numpy array. — hpaulj
– hpaulj, Commented Jul 10, 2019 at 0:02
np.empty(1) creates an array with space for 1 float element. You can only fill it with a scalar. — hpaulj
– hpaulj, Commented Jul 10, 2019 at 0:04

kierabeth · Accepted Answer · 2019-07-09 23:27:31Z

1

You could take the column and turn it into a numpy array using the following:

a = np.array(df['Col_A'])

answered Jul 9, 2019 at 23:27

kierabeth

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