In this tutorial, we will look at how to compute the set difference in Python with the help of some examples.

## What is Set Difference?

The set difference operation between two sets, for example `A - B`

, gives us the elements of set A which are not in set B. Let’s look at an example.

You can see that the resulting set from the `A - B`

operation contains only the elements of set A which are not in set B.

Note that the set difference operation is not commutative. That is, `A - B`

is not the same as `B - A`

which results in a set containing the elements of B which are not in A. For example, computing `B - A`

in the above example results in –

Thus, the set differences `A - B`

and `B - A`

are different from one another and may or may not be equal.

## Set Difference in Python

Python comes with a built-in set data structure to implement a set. It also has a number of additional functions to help you with common operations on sets such as union, intersection, difference, etc.

### Difference of two sets

To get the difference between two sets in Python, you can use the set `difference()`

function. The following is the syntax:

# set difference operation a - b a.difference(b)

It returns a new set containing the elements of a which are not in b.

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# create two sets a = {1,2,3} b = {3,7,2,6} # set difference a - b a.difference(b)

Output:

{1}

We get the resulting set as {1} as 1 is the only element in set a which is not present in set b.

### Using the subtraction `"-"`

operator for difference sets

Alternatively, you can also use the subtraction operator `-`

to compute set differences in Python. For example –

# alternative method print(a - b)

Output:

{1}

We get the same result as above.

Note that the `-`

operator for set difference only works on sets where as you can pass other iterables like lists, tuples, etc. to the set `difference()`

function.

### Set difference of more than two sets

You can also get the difference between more than two sets. You can use the following syntax.

# difference of more than two sets, for example, a,b,c,d a.difference(b,c,d)

Pass the sets (apart from the first one) as arguments to the `difference()`

function. It returns a set containing the elements in set a which are not present in any of the passed sets. Let’s look at an example.

# create four sets a = {1,2,3,5,8} b = {2,4,6} c = {0,1,2,7} d = {2,3,4} # elements of set a not in b, c, and d a.difference(b,c,d)

Output:

{5, 8}

We get the resulting set as {5, 8} since 5 and 8 are the only elements in set a which are not present in the sets b, c, and d.

You can also use the `-`

operator for set differences involving more than two sets.

# alternative method print(a-b-c-d)

Output:

{8, 5}

We get the same result as above (note that sets are not ordered).

You might also be interested in –

- Numpy – Set difference between two arrays
- Python – Get Union of Two or more Sets
- Python – Intersection of two or more Sets

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