Python Polars: The Definitive Guide

Chapter 8. Continuing Expressions

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In the previous chapter you learned how to begin an expression from scratch. A bare expression only gets you so far. In this chapter, you’ll learn how to continue an expression by adding additional operations (or methods).

More specifically, you’ll learn how to:

• Perform mathematical transformations

• Work with missing values

• Apply smoothing to values

• Select specific values

• Summarize values using statistics

A Plethora of Methods

There are more than 138 methods discussed in this chapter. It’s not possible to explain and demonstrate every single method in full detail. Please refer to the Polars API Reference for more details and examples.

For some code snippets in this chapter we use the math and numpy modules for accessing certain constants, such as math.pi, and for generating random values:

import math
import numpy as np

print(f"{math.pi=}")
rng = np.random.default_rng(1729)
print(f"{