247 – Lazy imports

247 – Lazy imports#

Lazy imports are coming to Python 3.15, with the new keyword lazy. An import statement that starts with the keyword lazy becomes a lazy import.

Suppose you define the toy module mod.py:

print("Hey!")

def f():
    return "Bye!"

The call to the function print at the top-level should run when the module is imported, in a regular import:

import mod
# Hey!

If you use the keyword lazy, you defer the execution of the module until the module is first used:

lazy import mod

mod.f()
# Hey!
# Bye!

Note how the top-level call to print was only executed when the module mod was referenced the first time. For the purposes of lazy imports, as soon as the module is referenced, it’s executed:

lazy import mod

a = mod
# Hey!

In the snippet above, just referencing the module mod to assign it to the variable a triggered the module’s execution.