Assume that `S`

and `T`

are assigned sets. Without using the join operator `|`

, how can I find the union of the two sets? This, for example, finds the intersection:

```
S = {1, 2, 3, 4}
T = {3, 4, 5, 6}
S_intersect_T = { i for i in S if i in T }
```

So how can I find the union of two sets in one line without using `|`

?

Assuming you also can't use `s.union(t)`

, which is equivalent to `s | t`

, you could try

```
>>> from itertools import chain
>>> set(chain(s,t))
set([1, 2, 3, 4, 5, 6])
```

Or, if you want a comprehension,

```
>>> {i for j in (s,t) for i in j}
set([1, 2, 3, 4, 5, 6])
```

You could use `or_`

alias:

```
>>> from operator import or_
>>> from functools import reduce # python3 required
>>> reduce(or_, [{1, 2, 3, 4}, {3, 4, 5, 6}])
set([1, 2, 3, 4, 5, 6])
```

If by join you mean union, try this:

```
set(list(s) + list(t))
```

It's a bit of a hack, but I can't think of a better one liner to do it.

You can do `union`

or simple list comprehension

```
[A.add(_) for _ in B]
```

A would have all the elements of B

Suppose you have 2 lists

```
A = [1,2,3,4]
B = [3,4,5,6]
```

so you can find `A`

Union `B`

as follow

```
union = set(A).union(set(B))
```

also if you want to find intersection and non-intersection you do that as follow

```
intersection = set(A).intersection(set(B))
non_intersection = union - intersection
```

If you are fine with modifying the original set (which you may want to do in some cases), you can use `set.update()`

:

```
S.update(T)
```

The return value is `None`

, but `S`

will be updated to be the union of the original `S`

and `T`

.

You can use union method for sets: `set.union(other_set)`

Note that it returns a new set i.e it doesn't modify itself.

You can just unpack both sets into one like this:

```
>>> set_1 = {1, 2, 3, 4}
>>> set_2 = {3, 4, 5, 6}
>>> union = {*set_1, *set_2}
>>> union
{1, 2, 3, 4, 5, 6}
```

The `*`

unpacks the set. Unpacking is where an iterable (e.g. a set or list) is represented as every item it yields. This means the above example simplifies to `{1, 2, 3, 4, 3, 4, 5, 6}`

which then simplifies to `{1, 2, 3, 4, 5, 6}`

because the set can only contain unique items.

Source: Stackoverflow.com