Operators: +, >>

Plotnine overloads the + and >> operators to make it easier to compose and pass data to plots.

from plotnine import *
from plotnine.data import mpg

The + operator

Use + to add geoms, scales, and themes to a plot.

(
    ggplot(mpg, aes("displ", "hwy"))
    + geom_point(aes(fill="class"))  # first geom
    + theme_minimal()  # theme
)

The >> operator

Use the >> operator to pipe data into a plot.

(
    mpg
    # piped into plot
    >> ggplot(aes("displ", "hwy", fill="class")) + geom_point()
)

Why operators?

Composable and extendable

Operators enable plot actions to use syntax that’s composable and extendable. This means two things:

• composable: you can add additional components like geoms to a plot.
• extendable: components defined in other libraries—like new kinds of geoms—can be added to a plot using the same + syntax.

For example, suppose you defined your own Plotnine theme, as shown below:

def my_theme(base_size=11):
    return (
        theme_grey(base_size=base_size)  # start with grey theme
        + theme(axis_text_x=element_text(angle=90))  # customize x-axis
    )

You can use this theme with the + operator, just like the built-in Plotnine themes:

(
    ggplot(mpg, aes("displ", "hwy", fill="class"))
    + geom_point()
    + my_theme(base_size=16)  # apply custom theme
)

Notice that the custom my_theme() component was added to the plot, in the same way anything else is (e.g. geom_point()).

Keep method chains going

The >> operator allows you to keep method chains going, without needing to create intermediate variables. This is especially useful when using Polars DataFrames, where you often want to do small bits of data wrangling before piping into the plot.

import polars as pl

pl_mpg = pl.from_pandas(mpg)

(
    pl_mpg
    #
    # label high mpg cars
    .with_columns(good_mpg=pl.col("hwy") > 30)
    #
    # remove compact cars
    .filter(pl.col("class") != "compact")
    #
    # pipe into plot
    >> ggplot(aes("displ", "hwy", fill="good_mpg")) + geom_point()
)