Python⇒Speed: Pandas vectorization: faster code, slower code, bloated memory

When you’re processing data with Pandas, so-called “vectorized” operations can significantly speed up your code. Or at least, that’s the theory.

In practice, in some situations Pandas vectorized operations can actually make your code slower, or at least no faster. And they can also significantly increase memory usage.

Let’s dig in and see what vectorization means in Pandas, when and why it helps, and when it’s harmful.