Filter rows in polars dataframe

filter

If you are analyzing data with Polars, it is almost impossible to complete an analysis without filtering. Data analysis usually involves selecting some rows from a dataframe while excluding others. Below is a dataframe of students and their grades.

shape: (6, 2)

Student	Grade
str	i64
"Spencer"	93
"Emily"	88
"Hannah"	73
"Aria"	69
"Mona"	55
"Paige"	89

Filter for some row

To get the row showing the student with the highest grade, you can use the filter method together with the max function, as shown below:

(df
 .filter(pl.col('Grade') == pl.max('Grade'))
 )

shape: (1, 2)

Student	Grade
str	i64
"Spencer"	93

You can also use filter to get the opposite of a specified value by using the “not equal to” operator (!=):

(df
 .filter(pl.col('Grade') != pl.max('Grade'))
 )

shape: (5, 2)

Student	Grade
str	i64
"Emily"	88
"Hannah"	73
"Aria"	69
"Mona"	55
"Paige"	89

You can achieve the same result as in the previous example by using the negation symbol ~:

(df
 .filter(~(pl.col('Grade') == pl.max('Grade')))
 )

shape: (5, 2)

Student	Grade
str	i64
"Emily"	88
"Hannah"	73
"Aria"	69
"Mona"	55
"Paige"	89

Check out my Polars course to learn more clever ways to analyze your data.