Pandas Where – pd.DataFrame.where()

Pandas Where will replace values where your condition is False. It is useful when you have values that do not meet a criteria, and they need replacing.

We don’t often use this function, but it can be a handy one liner instead of iterating through a DataFrame or Series with.apply()

1. pd.DataFrame.where(cond=condition_to_check, other="Value To Fill")

Pseudo code: Where a condition is false, replace a value.

Pandas Where

Where

.where() has two main parameters, cond and other. Both of these are flexible to take Series, DataFrame or callable.

• cond: Which stands for condition. This can either be a Series, DataFrame, or callable (function). WHERE this condition is false, pandas will replace values. I know, it’s a bit counter intuitive.
• Other What to replace your values with. This again can be a scalar (single value), Series, DataFrame, or callable.
• Other Parameters: To check out the other parameters that are not used that often, see the official documentation.

Let’s run through each iteration of the above parameters

Link to code

Official Documentation