[Python-ideas] __dir__ in which folder is this py file

Steven D'Aprano steve at pearwood.info
Mon May 7 06:44:36 EDT 2018

On Sun, May 06, 2018 at 09:33:03PM -0700, Nathaniel Smith wrote:

> How is
> data_path = __filepath__.parent / "foo.txt"
> more distracting than
> data_path = joinpath(dirname(__file__), "foo.txt")

Why are you dividing by a string? That's weird.

[looks up the pathlib docs]

Oh, that's why. It's still weird.

So yes, its very distracting.

First I have to work out what __filepath__ is, then I have to remember 
the differences between all the various flavours of pathlib.<whatever>Path 
and suffer a moment or two of existential dread as I try to work out 
whether or not *this* specific flavour is the one I need. This might not 
matter for heavy users of pathlib, but for casual users, it's a big, 
intimidating API with:

- an important conceptual difference between pure paths and
  concrete paths;
- at least six classes;
- about 50 or so methods and properties

As far as performance goes, I don't think it matters that we could 
technically make pathlib imported lazily. Many people put all their 
pathname manipulations at the beginning of their script, so lazy or not, 
the pathlib module is going to be loaded *just after* startup, .

For many scripts, this isn't going to matter, but for those who want to 
avoid the overhead of pathlib, making it lazy doesn't help. That just 
delays the overhead, it doesn't remove it.


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