# median() function in Python statistics module

Python is a very popular language when it comes to data analysis and statistics. Luckily, Python3 provide statistics module, which comes with very useful functions like mean(), median(), mode() etc.**median()** function in the statistics module can be used to calculate median value from an unsorted data-list. The biggest advantage of using median() function is that the data-list does not need to be sorted before being sent as parameter to the median() function.

Median is the value that separates the higher half of a data sample or probability distribution from the lower half. For a dataset, it may be thought of as the middle value. The median is the measure of the central tendency of the properties of a data-set in statistics and probability theory. Median has a very big advantage over Mean, which is the median value is not skewed so much by extremely large or small values. The median value is either contained in the data-set of values provided or it doesn’t sway too much from the data provided.

For *odd* set of elements, the median value is the middle one.

For *even* set of elements, the median value is the mean of two middle elements.

Median can be represented by the following formula :

Syntax :median([data-set])Parameters :[data-set]: List or tuple or an iterable with a set of numeric valuesReturns :Return the median (middle value) of the iterable containing the dataExceptions :StatisticsErroris raised when iterable passed is empty or when list is null.

**Code #1 :** Working

## Python3

`# Python code to demonstrate the ` `# working of median() function.` `# importing statistics module` `import` `statistics` `# unsorted list of random integers` `data1 ` `=` `[` `2` `, ` `-` `2` `, ` `3` `, ` `6` `, ` `9` `, ` `4` `, ` `5` `, ` `-` `1` `]` `# Printing median of the` `# random data-set` `print` `(` `"Median of data-set is : % s "` ` ` `%` `(statistics.median(data1)))` |

**Output :**

Median of data-set is : 3.5

**Code #2 :**

## Python3

`# Python code to demonstrate the` `# working of median() on various` `# range of data-sets` `# importing the statistics module` `from` `statistics ` `import` `median` `# Importing fractions module as fr` `from` `fractions ` `import` `Fraction as fr` `# tuple of positive integer numbers` `data1 ` `=` `(` `2` `, ` `3` `, ` `4` `, ` `5` `, ` `7` `, ` `9` `, ` `11` `)` `# tuple of floating point values` `data2 ` `=` `(` `2.4` `, ` `5.1` `, ` `6.7` `, ` `8.9` `)` `# tuple of fractional numbers` `data3 ` `=` `(fr(` `1` `, ` `2` `), fr(` `44` `, ` `12` `),` ` ` `fr(` `10` `, ` `3` `), fr(` `2` `, ` `3` `))` `# tuple of a set of negative integers` `data4 ` `=` `(` `-` `5` `, ` `-` `1` `, ` `-` `12` `, ` `-` `19` `, ` `-` `3` `)` `# tuple of set of positive` `# and negative integers` `data5 ` `=` `(` `-` `1` `, ` `-` `2` `, ` `-` `3` `, ` `-` `4` `, ` `4` `, ` `3` `, ` `2` `, ` `1` `)` `# Printing the median of above datasets` `print` `(` `"Median of data-set 1 is % s"` `%` `(median(data1)))` `print` `(` `"Median of data-set 2 is % s"` `%` `(median(data2)))` `print` `(` `"Median of data-set 3 is % s"` `%` `(median(data3)))` `print` `(` `"Median of data-set 4 is % s"` `%` `(median(data4)))` `print` `(` `"Median of data-set 5 is % s"` `%` `(median(data5)))` |

**Output :**

Median of data-set 1 is 5 Median of data-set 2 is 5.9 Median of data-set 3 is 2 Median of data-set 4 is -5 Median of data-set 5 is 0.0

**Code #3 :** Demonstrating StatisticsError

## Python3

`# Python code to demonstrate` `# StatisticsError of median()` `# importing the statistics module` `from` `statistics ` `import` `median` `# creating an empty data-set` `empty ` `=` `[]` `# will raise StatisticsError` `print` `(median(empty))` |

**Output :**

Traceback (most recent call last): File "/home/3c98774036f97845ee9f65f6d3571e49.py", line 12, in print(median(empty)) File "/usr/lib/python3.5/statistics.py", line 353, in median raise StatisticsError("no median for empty data") statistics.StatisticsError: no median for empty data

**Applications :**

For practical applications, different measures of dispersion and population tendency are compared on the basis of how well the corresponding population values can be estimated. For example, a comparison shows that the sample mean is more statistically efficient than the sample median when the data is uncontaminated by data from heavily-tailed data distribution or from mixtures of data distribution, but less efficient otherwise and that the efficiency of the sample median is higher than that for a wide range of distributions. To be more specific, the median has 64% efficiency compared to minimum-variance-mean ( for large normal samples ).