# Python program to get all subsets of given size of a set

Given a set, write a Python program to generate all possible subset of size* n* of given set within a list.

**Examples:**

Input :{1, 2, 3}, n = 2Output :[{1, 2}, {1, 3}, {2, 3}]Input :{1, 2, 3, 4}, n = 3Output :[{1, 2, 3}, {1, 2, 4}, {1, 3, 4}, {2, 3, 4}]

We have already discussed the same problem using the Naive approach in this article. This article focuses on the Pythonic approaches to Print all subsets of a given size of a set.

Python has **itertools.combinations(iterable, n)** which Return *n* length subsequences of elements from the input iterable. This can be used to Print all subsets of a given size of a set. Now, we have various alternatives to use this function.

**Code #1 : **

Simply pass the set as iterable and the size as arguments in the itertools.combinations() to directly fetch the combination list.

## Python3

`# Python Program to Print` `# all subsets of given size of a set` `import` `itertools` `def` `findsubsets(s, n):` ` ` `return` `list` `(itertools.combinations(s, n))` `# Driver Code` `s ` `=` `{` `1` `, ` `2` `, ` `3` `}` `n ` `=` `2` `print` `(findsubsets(s, n))` |

**Output:**

[(1, 2), (1, 3), (2, 3)]

**Code #2 : **

We can also use an alternative to the above-discussed method which is *mapping *set to itertools.combinations() function.

## Python3

`# Python Program to Print` `# all subsets of given size of a set` `import` `itertools` `from` `itertools ` `import` `combinations, chain` `def` `findsubsets(s, n):` ` ` `return` `list` `(` `map` `(` `set` `, itertools.combinations(s, n)))` ` ` `# Driver Code` `s ` `=` `{` `1` `, ` `2` `, ` `3` `}` `n ` `=` `2` `print` `(findsubsets(s, n))` |

**Output:**

[{1, 2}, {1, 3}, {2, 3}]

**Code #3 : **

Another method is to use for loop in itertools.combinations() function and append the combination sets to the list.

## Python3

`# Python Program to Print` `# all subsets of given size of a set` `import` `itertools` `# def findsubsets(s, n):` `def` `findsubsets(s, n):` ` ` `return` `[` `set` `(i) ` `for` `i ` `in` `itertools.combinations(s, n)]` ` ` `# Driver Code` `s ` `=` `{` `1` `, ` `2` `, ` `3` `, ` `4` `}` `n ` `=` `3` `print` `(findsubsets(s, n))` |

**Output:**

[{1, 2, 3}, {1, 2, 4}, {1, 3, 4}, {2, 3, 4}]

**Code #4:**

Many a time when this question is asked in interviews, it’s better to answer without using any module. So, here is the solution that does not use itertools module:

## Python3

`def` `subsets(numbers):` ` ` `if` `numbers ` `=` `=` `[]:` ` ` `return` `[[]]` ` ` `x ` `=` `subsets(numbers[` `1` `:])` ` ` `return` `x ` `+` `[[numbers[` `0` `]] ` `+` `y ` `for` `y ` `in` `x]` `# wrapper function` `def` `subsets_of_given_size(numbers, n):` ` ` `return` `[x ` `for` `x ` `in` `subsets(numbers) ` `if` `len` `(x)` `=` `=` `n]` `if` `__name__ ` `=` `=` `'__main__'` `:` ` ` `numbers ` `=` `[` `1` `, ` `2` `, ` `3` `, ` `4` `]` ` ` `n ` `=` `3` ` ` `print` `(subsets_of_given_size(numbers, n))` |

**Output:**

[[2, 3, 4], [1, 3, 4], [1, 2, 4], [1, 2, 3]]

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