tidypolars 0.2.2

Tidy interface to polars

tidypolars

tidypolars is a data frame library built on top of the blazingly fast polars library that gives access to methods and functions familiar to R tidyverse users.

Installation

$ pip3 install tidypolars

General syntax

tidypolars methods are designed to work like tidyverse functions:

import tidypolars as tp
from tidypolars import col, desc

df = tp.Tibble(x = range(3), y = range(3, 6), z = ['a', 'a', 'b'])

(
    df
    .select('x', 'y', 'z')
    .filter(col('x') < 4, col('y') > 1)
    .arrange(desc('z'), 'x')
    .mutate(double_x = col('x') * 2,
            x_plus_y = col('x') + col('y'))
)
┌─────┬─────┬─────┬──────────┬──────────┐
│ x   ┆ y   ┆ z   ┆ double_x ┆ x_plus_y │
│ --- ┆ --- ┆ --- ┆ ---      ┆ ---      │
│ i64 ┆ i64 ┆ str ┆ i64      ┆ i64      │
╞═════╪═════╪═════╪══════════╪══════════╡
│ 2   ┆ 5   ┆ b   ┆ 4        ┆ 7        │
├╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌┤
│ 0   ┆ 3   ┆ a   ┆ 0        ┆ 3        │
├╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌┤
│ 1   ┆ 4   ┆ a   ┆ 2        ┆ 5        │
└─────┴─────┴─────┴──────────┴──────────┘

The key difference from R is that column names must be wrapped in col() in the following methods:

• .filter()
• .mutate()
• .summarize()

The general idea - when doing calculations on a column you need to wrap it in col(). When doing simple column selections (like in .select()) you can pass the column names as strings.

Group by syntax

Methods operate by group by calling the by arg.

• A single column can be passed with by = 'z'
• Multiple columns can be passed with by = ['y', 'z']

(
    df
    .summarize(avg_x = tp.mean(col('x')),
               by = 'z')
)
┌─────┬───────┐
│ z   ┆ avg_x │
│ --- ┆ ---   │
│ str ┆ f64   │
╞═════╪═══════╡
│ a   ┆ 0.5   │
├╌╌╌╌╌┼╌╌╌╌╌╌╌┤
│ b   ┆ 2     │
└─────┴───────┘

Selecting/dropping columns

tidyselect functions can be mixed with normal selection when selecting columns:

df = tp.Tibble(x1 = range(3), x2 = range(3), y = range(3), z = range(3))

df.select(tp.starts_with('x'), 'z')
┌─────┬─────┬─────┐
│ x1  ┆ x2  ┆ z   │
│ --- ┆ --- ┆ --- │
│ i64 ┆ i64 ┆ i64 │
╞═════╪═════╪═════╡
│ 0   ┆ 0   ┆ 0   │
├╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌┤
│ 1   ┆ 1   ┆ 1   │
├╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌┤
│ 2   ┆ 2   ┆ 2   │
└─────┴─────┴─────┘

To drop columns use the .drop() method:

df.drop(tp.starts_with('x'), 'z')
┌─────┐
│ y   │
│ --- │
│ i64 │
╞═════╡
│ 0   │
├╌╌╌╌╌┤
│ 1   │
├╌╌╌╌╌┤
│ 2   │
└─────┘

Converting to/from pandas data frames

If you need to use a package that requires pandas data frames, you can convert from a tidypolars Tibble to a pandas DataFrame.

To do this you'll first need to install pyarrow:

pip3 install pyarrow

To convert to a pandas DataFrame:

df = df.to_pandas()

To convert from a pandas DataFrame to a tidypolars Tibble:

df = tp.from_pandas(df)

Speed Comparisons

A few notes:

• Comparing times from separate functions typically isn't very useful. For example - the .summarize() tests were performed on a different dataset from .pivot_wider().
• All tests are run 5 times. The times shown are the median of those 5 runs.
• All timings are in milliseconds.
• All tests can be found in the source code here.
• FAQ - Why are some tidypolars functions faster than their polars counterpart?
  • Short answer - they're not! After all they're just using polars in the background.
  • Long answer - All python functions have some slight natural variation in their execution time. By chance the tidypolars runs were slightly shorter on those specific functions on this iteration of the tests. However one goal of these tests is to show that the "time cost" of translating syntax to polars is very negligible to the user (especially on medium-to-large datasets).
• Lastly I'd like to mention that these tests were not rigorously created to cover all angles equally. They are just meant to be used as general insight into the performance of these packages.

┌─────────────┬────────────┬─────────┬──────────┐
│ func_tested ┆ tidypolars ┆ polars  ┆ pandas   │
│ ---         ┆ ---        ┆ ---     ┆ ---      │
│ str         ┆ f64        ┆ f64     ┆ f64      │
╞═════════════╪════════════╪═════════╪══════════╡
│ arrange     ┆ 190.345    ┆ 169.478 ┆ 500.112  │
├╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌┤
│ case_when   ┆ 87.348     ┆ 79.427  ┆ 152.623  │
├╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌┤
│ distinct    ┆ 16.888     ┆ 16.282  ┆ 28.725   │
├╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌┤
│ filter      ┆ 29.789     ┆ 29.91   ┆ 231.397  │
├╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌┤
│ full_join   ┆ 236.784    ┆ 231.283 ┆ 1042.689 │
├╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌┤
│ inner_join  ┆ 49.71      ┆ 47.563  ┆ 630.98   │
├╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌┤
│ left_join   ┆ 113.792    ┆ 115     ┆ 1100.607 │
├╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌┤
│ mutate      ┆ 7.979      ┆ 7.408   ┆ 117.283  │
├╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌┤
│ pivot_wider ┆ 42.764     ┆ 39.939  ┆ 49.048   │
├╌╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌┤
│ summarize   ┆ 59.434     ┆ 58.011  ┆ 453.707  │
└─────────────┴────────────┴─────────┴──────────┘

Contributing

Interested in contributing? Check out the contributing guidelines. Please note that this project is released with a Code of Conduct. By contributing to this project, you agree to abide by its terms.