### Question :

Is this the best way to add an extra dimension to a numpy array in one line of code?

If k is an numpy array of an arbitrary shape, so `k.shape = (s1, s2, s3, ..., sn)`

, and I want to reshape it so that `k.shape`

becomes `(s1, s2, ..., sn, 1)`

, is this the best way to do it in one line?

```
k.reshape(*(list(k.shape) + [1])
```

##
Answer #1:

It’s easier like this:

```
k.reshape(k.shape + (1,))
```

But if all you want is to add an empty dimension at the end, you should use `numpy.newaxis`

:

```
import numpy as np
k = k[..., np.newaxis]
```

or

```
k = k[..., None]
```

(See the documentation on slicing).

##
Answer #2:

You can use numpy.expand_dims

```
In [4]: import numpy as np
In [5]: a = [1,2,3,4]
In [6]: np.expand_dims(a, axis=1)
Out[6]:
array([[1],
[2],
[3],
[4]])
```