Hello coders, today we are going to solve **Iterables and Iterators HackerRank Solution** in **Python**.

**Task**

The *itertools* module standardizes a core set of fast, memory efficient tools that are useful by themselves or in combination. Together, they form an *iterator algebra* making it possible to construct specialized tools succinctly and efficiently in pure *Python*.

You are given a list of ** N** lowercase English letters. For a given integer

**, you can select any**

*K***indices (assume**

*K***1**-based indexing) with a uniform probability from the list.

Find the *probability* that *at least* one of the ** K** indices selected will contain the letter: ‘

**‘.**

*a***Input Format**

The input consists of three lines. The first line contains the integer ** N**, denoting the length of the list. The next line consists of

**space-separated lowercase English letters, denoting the elements of the list.**

*N*The third and the last line of input contains the integer * K*, denoting the number of indices to be selected.

**Output Format**

Output a single line consisting of the *probability* that *at least* one of the ** K** indices selected contains the letter:’

**‘.**

*a***Note**: The answer must be correct up to 3 decimal places.

**Constraints**

**1 <=***N*<= 10**1 <=***K*<=*N**All the letters in the list are lowercase English letters.*

**Sample Input**

```
4
a a c d
2
```

**Sample Output**

`0.8333`

**Explanation**

All possible unordered tuples of length **2** comprising of indices from **1** to **4** are:**(1, 2), (1, 3), (1, 4), (2, 3), (2, 4), (3, 4)**

Out of these **6** combinations, **5** of them contain either index **1** or index **2** which are the indices that contain the letter ‘* a*‘.

Hence, the answer is **5/6**.

**Solution – Iterables and Iterators in Python **

# Enter your code here. Read input from STDIN. Print output to STDOUT from itertools import combinations N = int(input()) LETTERS = list(input().split(" ")) K = int(input()) TUPLES = list(combinations(LETTERS, K)) CONTAINS = [word for word in TUPLES if "a" in word] print(len(CONTAINS)/len(TUPLES))

**Disclaimer:** The above Problem **(Iterables and Iterators)** is generated by **Hacker Rank** but the Solution is Provided by **CodingBroz**. This tutorial is only for **Educational** and **Learning** Purpose.