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# Python | Standard deviation of list

• Last Updated : 03 Oct, 2019

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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