Python's Hidden 'Import Tax' Slows Apps — New Fix Finally Arrives

You click a button, and your app takes a moment to open. That wait might not be your internet or your computer — it could be Python's hidden 'import tax.' Python is one of the most popular programming languages, but every time a Python program starts, it has to load (or 'import') its building blocks. The first major study of this cost found that while most small requests are fast, the slowest ones take over 350 milliseconds — enough for you to notice the lag.

Why does this matter for you? Because Python powers everything from command-line tools to website backends, and especially serverless apps that launch on demand. Those serverless functions 'cold start' every time someone uses them, so the import tax directly translates to slower responses and higher cloud bills for businesses. Big apps that load many parts suffer the most — some subpackages take up to 294 times longer to load than their top level, so what seems like a small tool can actually be painfully slow.

The good news: Python 3.15 introduces 'lazy imports,' a feature that delays loading until it's truly needed. The study shows this makes importing almost free. But there's a catch: 8 out of 414 popular packages break under this new mode. Most users won't notice, but developers of those tools will need to patch them.

The study also uncovered some surprises. Python keeps getting slower for the same code on Macs (about 16% per version generation), but not on Linux. And even tiny updates between versions can swing startup times by a third. For regular users, this all means your Python apps should get snappier soon — provided the bugs get worked out first.