luffe - 1 year ago 235

Python Question

For example: I have

`a = np.array([123, 412, 444])`

and

`b = np.array([123, 321])`

I want to know if

`a`

`b`

Answer

You can use set difference to determine what you are looking for. Numpy has a built-in function called numpy.setdiff1d(ar1, ar2):

Return the sorted, unique values in ar1 that are not in ar2.

Example for your case:

```
>>> a = np.array([123, 412, 444])
>>> b = np.array([123, 321])
>>> diff = np.setdiff1d(b, a)
>>> print diff
array([321])
>>> if diff.size:
>>> print "Not passed"
```

So for your case, you would do a set difference you would subtract a from b and obtain an array with elements in b which are not in a. Then you can check if that was empty or not. As you can see, the output is `312`

, which is an entry present in `a`

but not in `b`

; the length of it is now larger then zero, therefore there were elements in `b`

which were not present in `a`

.

Source (Stackoverflow)