Hilemonstoer - 9 months ago 80

Python Question

I would like a list of 2d numpy arrays (x,y) , where each x is in {-5, -4.5, -4, -3.5, ..., 3.5, 4, 4.5, 5} and the same for y.

I could do

`x = np.arange(-5, 5.1, 0.5)`

y = np.arange(-5, 5.1, 0.5)

and then iterate through all possible pairs, but I'm sure there's a nicer way...

I would like something back that looks like:

`[[-5, -5],`

[-5, -4.5],

[-5, -4],

...

[5, 5]]

but the order does not matter.

Answer

You can use `np.mgrid`

for this, it's often more convenient than `np.meshgrid`

because it creates the arrays in one step:

```
import numpy as np
X,Y = np.mgrid[-5:5.1:0.5, -5:5.1:0.5]
```

For linspace-like functionality, replace the step (i.e. `0.5`

) with a complex number whose magnitude specifies the number of points you want in the series. Using this syntax, the same arrays as above are specified as:

```
X, Y = np.mgrid[-5:5:21j, -5:5:21j]
```

You can then create your pairs as:

```
xy = np.vstack((X.flatten(), Y.flatten())).T
```

As @ali_m suggested, this can all be done in one line:

```
xy = np.mgrid[-5:5.1:0.5, -5:5.1:0.5].reshape(2,-1).T
```

Best of luck!

Source (Stackoverflow)