What is ffill and bfill in pandas?
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What is ffill and bfill in pandas?

What is ffill and bfill in pandas?

This recipe explains what is ffill and bfill in pandas

Recipe Objective

bfill() is used to backward fill the missing values in the dataset. It will backward fill the NaN values that are present in the pandas dataframe. ffill() function is used forward fill the missing value in the dataframe.

So this recipe is a short example on What is ffill and bfill in pandas. Let's get started.

Step 1 - Import the library

import pandas as pd

Let's pause and look at these imports. Pandas is generally used for performing mathematical operation and preferably over arrays.

Step 2 - Setup the Data

df = pd.DataFrame({"A":[None, 1, 2, 3, None, None], "B":[11, 5, None, None, None, 8], "C":[None, 5, 10, 11, None, 8]}) print(df)

Here we have setup a random dataset with some None values in it.

Step 3 - Apply bfill() and ffill()

print(df.ffill(axis = 0) ) print(df.bfill(axis =0) )

Here we are applied forward fill and backward fill on our dataframe on columns. Now, forward fill taken from above rows in similar column and fill it in later. Similar is for bfill.

Step 4 - Let's look at our dataset now

Once we run the above code snippet, we will see:

Scroll down to the ipython file to look at the results.

We can see the difference in ffill and bfill while being applied at our dataset.

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