If you already worked with time-series data, let me tell you a bit more about the **cumulative sum function.**

The cumulative sum function is extremely helpful when you want to know what is the sum of a variable over time.

Let me give you an example with E-commerce sales data.

**So far so good!**

Now that we have the sales volume per month in USD. One could ask the question how much total sales volume have we done so far.

Using the **DataFrame.cumsum()**** **we can compute that metric over time.

## In Python

Resulting such DataFrame:

And if we plot it,

Here you are! You now know how to compute the cumulative sum of a column with Pandas in Python.

# More on DataFrames

If you want to know more about DataFrame and Pandas. Check out the other articles I wrote on the topic, just here :