CODEWITHSUNDEEP
pythonarraysnumpy
dpeng
dpeng

Reputation: 487

Numpy append to an empty array

1st case :

>>> import numpy as np
>>> x=np.array(0)
>>> x=np.append(x,1)
>>> x
array([0, 1])

x contains 2 elements. Why is that ?!

2nd case :

>>> x=np.array([])
>>> x=np.append(x,1)
>>> x
array([ 1.])

x contains 1 element, as expected.

What's the difference between np.array(0) and np.array([]) ?

Upvotes: 5

Views: 14337

Answers (1)

Srivatsan
Srivatsan

Reputation: 9363

In your first case, you are creating an array called x that will containing one value, which is 0.

In your second case you are creating an empty array called x that will contain no values, but is still an array.

FIRST CASE

So when you append x = np.append(x,1), the value 1 get's appended to your array (which already contains 0) i.e. it now contains 0 and 1

SECOND CASE

Since you have no values in the empty array, when you append x=np.append(x,1) the value 1 get's appended and the length of x becomes 1 (i.e. it now contains only 1)

P.S. I believe you might have thought that calling x = np.array(0) with the 0 would make it an empty array, it doesn't!! In Python, 0 is still taken to be a number and is appended to the array.

Upvotes: 7

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