I am trying to create a new column in Polars data frame based on comparison of two existing columns: import polars as pl data = {"a": [2, 30], "b": [20, 3]} df = pl.DataFrame(data) df Out[4]: shape: (2, 2) ┌─────┬─────┐ │ a ┆ b │ │ — ┆ — │ │ i64 ┆ i64 │… Read More python polars: new column based on condition/comparison of two existing columns

Being a new user to polars coming from pandas, I have searched polars GitHub pages, user guide, stackoverflow and discord channel on how to add a new column to a polars dataframe. I have only found polars examples on how to add new columns based on existing ones. How should the following pandas example be… Read More Add new column to polars DataFrame

Does polars have the function to encode string column into integers (1, 2, 3) like pandas.factorize? Didn’t find it in the polars documentation >Solution : Perhaps you’re looking for a dense rank or the categorical type. df = pl.DataFrame({"column": ["foo", "bar", "baz", "foo", "foo"]}) df.with_columns(rank = pl.col("column").rank("dense")) shape: (5, 2) ┌────────┬──────┐ │ column | rank… Read More Polars equivalent of pandas factorize

I have a polars DataFrame with a bunch of columns. One of them has datetime values (for example hourly data from 2017 – 2019). How can I replace the year of all the datetime values with a year I specify? Original Datetime Column: shape: (26280, 1) Index datetime[ns] 2017-01-01 00:00:00 2017-01-01 01:00:00 2017-01-01 02:00:00 2017-01-01… Read More Polars: Replace the Year in a DataFrame's Datetime Column

This code is pandas. pandas_reserve_tb \ .groupby([‘hotel_id’, ‘people_num’])[‘total_price’] \ .sum().reset_index() I would like to change this code to polars. polars_researve_tb \ .groupby("hotel_id", "people_num")[‘total_price’] \ .sum().with_row_count() But, I got the error "TypeError: ‘GroupBy’ object is not subscriptable" How to solove this error? >Solution : You probably meant polars_researve_tb \ .groupby(["hotel_id", "people_num"]).agg(pl.col(‘total_price’).sum()) I’d advise posting reproducible examples… Read More How to change this code to polars ?" TypeError: 'GroupBy' object is not subscriptable"

I’m trying to build a histogram of some data in polars. As part of my histogram code, I need to duplicate some rows. I’ve got a column of values, where each row also has a weight that says how many times the row should be added to the histogram. How can I duplicate my value… Read More Create duplicates of row based column values

I am trying to count the number of letters in a string in Polars. I could probably just use an apply method and get the len(Name). However, I was wondering if there is a polars specific method? import polars as pl mydf = pl.DataFrame( {"start_date": ["2020-01-02", "2020-01-03", "2020-01-04"], "Name": ["John", "Joe", "James"]}) print(mydf) │start_date ┆… Read More Python Polars find the length of a string in a dataframe

I am using Polars in Python to try and add thirty days to a date I run the code, get no errors but also get no new dates Can anyone see my mistake? import polars as pl mydf = pl.DataFrame( {"start_date": ["2020-01-02", "2020-01-03", "2020-01-04"]}) mydf = mydf.with_column( pl.col("start_date").str.strptime(pl.Date, "%Y-%m-%d"), ) # Generate the days above… Read More Polars Adding Days to a date

I am trying to pick up the package polars from Python. I come from an R background so appreciate this might be an incredibly easy question. I want to implement a case statement where if any of the conditions below are true, it will flag it to 1 otherwise it will be 0. My new… Read More Polars Case Statement

I would like to store in an object (a list, a dictionary or whatever) many different filters, and then be able to select the ones I want and evaluate them in the .filter() method. Below is an example: # Sample DataFrame df = pl.DataFrame( {"col_a": [1, 2, 3, 4, 5, 6, 7, 8, 9, 10],… Read More How to list, concatenate, and evaluate polars expressions?