In keeping with the "There's only one obvious way to do it", how do you get the magnitude of a vector (1D array) in Numpy?

```
def mag(x):
return math.sqrt(sum(i**2 for i in x))
```

The above works, but I *cannot believe* that I must specify such a trivial and core function myself.

The function you're after is `numpy.linalg.norm`

. (I reckon it should be in base numpy as a property of an array -- say `x.norm()`

-- but oh well).

```
import numpy as np
x = np.array([1,2,3,4,5])
np.linalg.norm(x)
```

You can also feed in an optional `ord`

for the nth order norm you want. Say you wanted the 1-norm:

```
np.linalg.norm(x,ord=1)
```

And so on.