# Introduction to Aggregation Methods on Series Data in Python

Python, along with its robust libraries like Pandas, NumPy, and others, provides an efficient and effective platform for handling and manipulating series data. One of the key techniques that is often used when dealing with this type of data is "aggregation". Aggregation refers to any process where values of multiple rows are grouped together to form a single summary value. Today, we are going to explore ten common aggregation methods you can use with Python.

## Common Aggregation Methods in Python

1. Sum: Adds up all the values in the series.
2. Mean: Calculates the average of the series.
3. Median: Finds the middle value of the series.
4. Mode: Returns the most common value in the series.
5. Min: Returns the smallest value in the series.
6. Max: Returns the largest value in the series.
7. Count: Returns the number of non-null values in the series.
8. Std: Calculates the standard deviation of the series.
9. Var: Calculates the variance of the series.
10. Nunique: Returns the number of distinct elements in the series.

These methods are called using the syntax `Series.method()`. For example, to get the mean of a series 's', we would use `s.mean()`.

## Diving into an Example

Let's dive into an example where we use the `gt()`, `sum()`, and `mean()` methods to perform an analysis on a series 's'. Let's say we want to find the number of observations greater than a certain input number and what percentage of the data set these observations represent.

``````
number_input = some_number  # Replace 'some_number' with the actual number
observation_count = s.gt(number_input).sum()
percentage = s.gt(number_input).mean() * 100

result = 'There are {} observations greater than {}. '.format(observation_count, number_input)
result += 'Representing {:.1f}% of the entire data set.'.format(percentage)
``````

In this code, `s.gt(number_input)` creates a boolean series where each value is True if the corresponding value in 's' is greater than 'number_input' and False otherwise. Then `sum()` is used to count the number of True values (i.e., the number of observations greater than 'number_input'), and `mean()` calculates the proportion of True values, which is then multiplied by 100 to get the percentage.

Using aggregation methods like this allows us to quickly and easily generate insights from our data. Python’s expressive syntax and powerful libraries make these tasks a breeze.

I hope this post has helped you understand the concept of aggregation in Python better. Happy coding!