# 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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