Use relative (.xyz) and absolute (sssom.xyz) imports consistently

[matentzn]

See @cthoyt comment here.

[hrshdhgd]

I've seen both used but sometimes using relative imports causes issues when a module is imported. Any other opinions?

[cthoyt]

I prefer relative imports because it reminds you never to run packaged code as a script, except through the python -m interface. There are no practical differences in what is possible, though I think that using absolute imports allows people to make nonsensical imports, like doing from sssom import ... in a very deeply nested module -> e.g., it allows you to not think about the code and this can get you into circular import trouble

[matentzn]

I am happy either way, what you are saying makes sense, lets go with relative for now.. Thanks @cthoyt

[matentzn]

@joeflack4 had trouble getting sssom-py up and running for development.

Putting this decision up for another vote, here is the related SO thread:

https://stackoverflow.com/questions/4209641/absolute-vs-explicit-relative-import-of-python-module

@joeflack4 do you have any opinion?

[joeflack4]

Thanks, @matentzn . That thread you linked is one of a great many on this topic. Like most of those threads, the consensus is to use absolute imports.

I've been having difficulty getting the relative imports to work with PyCharm, both in this project and other projects. As for this project, I'm using Python 3.9. I tried virtualenv, virtualenvwrapper, and tox. I've got my PyCharm interpreter set up correctly for each of these cases, and my debug config looks good to me (more information/screenshots in #209). I tried both with and without setting "sssom/` as "sources root" in PyCharm. So far I'm having no luck.

---

I've been working with Python for awhile and I wasn't sure if I agreed with @cthoyt . That doesn't seem to line up with my experience with Python. I've always used absolute imports when running my packages using python -m <package-name>. I was unaware if by design relative imports were supposed to be friendlier towards that? Not my experience.

I also just did an experiment locally, and as I expected, running a script directly which uses absolute imports did not work for me.

pkg
├── __init__.py
├── __main__.py
├── a.py
├── b.py
└── c.py

python3 pkg/c.py
Traceback (most recent call last):
  File "/Users/joeflack4/Desktop/pkg/c.py", line 1, in <module>
    from pkg.a import x
ModuleNotFoundError: No module named 'pkg'

However, running as a module this way works fine whether I'm using absolute or relative in this specific case:

pkg/__main__.py:

from .b import x
from pkg.a import z

print(x)
print(z)

I assigned both x and z to 1, so this is what I expected:

python3 -m pkg
1
1

---

In any case, as I mentioned to Nico and Harshad, I've tried relative imports a number of times, and while relative imports make a lot of sense to me in theory, and I would prefer to use them if I could, they don't end up working out for me in a lot of situations. In the past, I've gotten them to work in some situations, but then if I hand my code to someone else with a different machine / project setup, or if I try running my code a different way, they don't always work. Meanwhile, I've found absolute imports to be very reliable. I think I've gotten them to work just about always.

So, my recommendation is absolute imports (unless we can figure out some magic to make relative imports work reliably everywhere).

[cthoyt]

I don't have a lot of energy/motivation for education at the moment, but the fact that you ran into this issue demonstrates that if you use the non-src/ layout, it's possible to run code outside of a packaged context, which again I posit is bad because it enables the developer to forget about how others will use the code.

Best next step would be to adopt the standard src/ layout for this repo, which we've been talking about for a while.

[matentzn]

@joeflack4 are you positive you cannot fix the problem in your setup? We do not have the time atm to change the SSSOM layout, and I also do not want to hastily push absolute package imports through now without a proper investigation..

[joeflack4]

@matentzn As I mentioned (maybe in another thread), I'll just debug using absolute imports, and change them back to relative before I submit a PR.

[matentzn]

If it aint too much of a pain... :) You know best!