What is DataFrame.filter in Polars?
Polars is a fast and efficient data manipulation library written in Rust. It is designed to provide high-performance operations on large datasets and handles them more quickly than pandas library.
Note: Learn more about the difference between the
polarsandpandaslibrary.
The filter() function
The DataFrame.filter() function is used to apply filtering conditions to the DataFrame and retrieve rows that satisfy our given conditions. It’s particularly useful when dealing with large datasets where we need to narrow down our data to the information that meets our requirements.
Syntax
Here is the syntax of the DataFrame.filter() function:
DataFrame.filter(condition)
condition: It can be comparisons, logical expressions, arithmetic operations, or column references that define which rows to be included in the filtered data.
Return value
The function returns a DataFrame, which contains the filtered rows according to the defined condition.
Code
Here is the coding example of the DataFrame.filter() method to filter the DataFrame in Polars:
import polars as pldf = pl.DataFrame({"Students": ["Joseph", "Danial", "Ema", "John"],"Calculus": [98, 85, 92, 67],"Data structures": [91, 89, 92, 55],"Operating system": [96, 88, 91, 62],})# Filtering rows on the base of one conditionprint(df.filter(pl.col("Students") == "Danial"))# Filtering rows on the base of AND conditionsprint(df.filter((pl.col("Calculus") > 90) & (pl.col("Data structures") > 90) & (pl.col("Operating system") > 90)))# Filtering rows on the base of OR conditionsprint(df.filter((pl.col("Calculus") < 60) | (pl.col("Data structures") < 60) | (pl.col("Operating system") < 60)))
Code explanation
Line 1: We import
polarslibrary aspl.Lines 2–9: We defined our DataFrame as
dffor the student’s score report in calculus, data structures, and operating system courses.Line 11: We used the
df.filter()function only to print the score report of the student named Danial.Line 14: We applied multiple conditions using the
&operator to find the students who scored greater than 90 in all courses.Line 17: We applied multiple conditions using the
|operator to find the students who scored less than 60 in any of the courses.
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