# Python | Standard deviation of list

Sometimes, while working with Mathematics, we can have a problem in which we intend to compute the standard deviation of a sample. This has many applications in competitive programming as well as school level projects. Let’s discuss certain ways in which this task can be performed.

Method #1 : Using `sum()` + list comprehension
This is a brute force shorthand to perform this particular task. We can approach this problem in sections, computing mean, variance and standard deviation as square root of variance. The `sum()` is key to compute mean and variance. List comprehension is used to extend the common functionality to each of element of list.

 `# Python3 code to demonstrate working of ` `# Standard deviation of list ` `# Using sum() + list comprehension ` ` `  `# initializing list ` `test_list ``=` `[``4``, ``5``, ``8``, ``9``, ``10``] ` ` `  `# printing list ` `print``(``"The original list : "` `+` `str``(test_list)) ` ` `  `# Standard deviation of list ` `# Using sum() + list comprehension ` `mean ``=` `sum``(test_list) ``/` `len``(test_list) ` `variance ``=` `sum``([((x ``-` `mean) ``*``*` `2``) ``for` `x ``in` `test_list]) ``/` `len``(test_list) ` `res ``=` `variance ``*``*` `0.5` ` `  `# Printing result ` `print``(``"Standard deviation of sample is : "` `+` `str``(res)) `

Output :

```
The original list : [4, 5, 8, 9, 10]
Standard deviation of sample is : 2.3151673805580453
```

Method #2 : Using `pstdev()`
This task can also be performed using inbuilt functionality of `pstdev()`. This function computes standard deviation of sample internally.

 `# Python3 code to demonstrate working of ` `# Standard deviation of list ` `# Using pstdev() ` `import` `statistics ` ` `  `# initializing list ` `test_list ``=` `[``4``, ``5``, ``8``, ``9``, ``10``] ` ` `  `# printing list ` `print``(``"The original list : "` `+` `str``(test_list)) ` ` `  `# Standard deviation of list ` `# Using pstdev() ` `res ``=` `statistics.pstdev(test_list) ` ` `  `# Printing result ` `print``(``"Standard deviation of sample is : "` `+` `str``(res)) `

Output :

```
The original list : [4, 5, 8, 9, 10]
Standard deviation of sample is : 2.3151673805580453
```

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