Implementation of fetch_pdb()

[jauy123]

Fixes #4907

Changes made in this Pull Request:

This is a still work in progress, but here's a implementation of @BradyAJohnston 's code wrapped into classes. I still need to write tests and docs for the entire thing.

• Added two classes: DownloaderBase and 'PDBDownloader' in order to implement downloading structure file from online sources such as the PDB databank.
• Added requests as a dependency
• mda.fetch_pdb() is implemented as a wrapper to commonly used option in 'PDBDownloader'

PR Checklist

• Issue raised/referenced?
• Tests updated/added?
• Documentation updated/added?
• package/CHANGELOG file updated?

Developers Certificate of Origin

I certify that I can submit this code contribution as described in the Developer Certificate of Origin, under the MDAnalysis LICENSE.

---

📚 Documentation preview 📚: https://mdanalysis--4943.org.readthedocs.build/en/4943/

[jauy123]

I'm not sure where to put this code in the codebase, so I create a new folder for it right now. I'm open to it being moved somewhere

Some stuff which I like to still add (besides tests and docs):

1. Verbose option for PdbDownloader.download() (I think tqdm was a dependency last time I saw?)
2. Integration with Mdanalysis' logger
3. Probably could wrap the cache logic into a separate function

[BradyAJohnston]

I think others will have to confirm, but likely we'll want to have requests be an optional dependency to reduce core library dependencies (as the fetching of structures won't be something that lot of users will be doing).

Additional it's not finalised yet but if the mmcif reader in #2367 gets finalised then the default download shouldn't be .pdb (but can remain for now).

[codecov]

Codecov Report

Attention: Patch coverage is 91.86047% with 7 lines in your changes missing coverage. Please review.

Project coverage is 93.40%. Comparing base (dcaa087) to head (651bf26).

Files with missing lines	Patch %	Lines
package/MDAnalysis/web/downloaders.py	91.02%	3 Missing and 4 partials ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #4943      +/-   ##
===========================================
- Coverage    93.42%   93.40%   -0.02%     
===========================================
  Files          177      193      +16     
  Lines        21859    23014    +1155     
  Branches      3078     3091      +13     
===========================================
+ Hits         20422    21497    +1075     
- Misses         986     1062      +76     
- Partials       451      455       +4     

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[jauy123]

I'm ok with that. I can make the code raise an exception if requests is not in the environment.

[jauy123]

Assuming that requests will be optional dependency, how would I exactly specify in the build files? Right now, I'm just hard coding it in, so that the github CLI tests can build successfully and run.

[BradyAJohnston]

You've added it to one of the optional dependency categories which is all that should be required. For the actual files where it is used you'll need to have something setup like the usage of biopython:

mdanalysis/package/MDAnalysis/analysis/align.py

Lines 200 to 207 in dcaa087

	try:
	import Bio.AlignIO
	import Bio.Align
	import Bio.Align.Applications
	except ImportError:
	HAS_BIOPYTHON = False
	else:
	HAS_BIOPYTHON = True

I'm not an expert on the pipelines so someone else would have to pitch in more on that.

[jauy123]

Thanks for the comment!

[jauy123]

I happen to have another question!

Is it normal for some of the tests to not be consistent across each commit? From what I understand, each github CLI has to get and build each MDAnalysis from source, and this instance can potentially timeout from what I observe across each commit.

The macOS (of the latest commit) failed at 97% of test because it reached the max wall time of two hours.

Even then the latest Azure tests failed because of other tests in the source code which I didn't write (namely due to other tests)

From Azure_Tests Win-Python310-64bit-full (commit 651bf267076d2d7da6491608b1b5136915caf2e2)

FAIL MDAnalysisTests/coordinates/test_h5md.py::TestH5MDReaderWithRealTrajectory::test_open_filestream - Issue #2884
XFAIL MDAnalysisTests/coordinates/test_h5md.py::TestH5MDWriterWithRealTrajectory::test_write_with_drivers[core] - occasional PermissionError on windows
XFAIL MDAnalysisTests/coordinates/test_memory.py::TestMemoryReader::test_frame_collect_all_same - reason: memoryreader allows independent coordinates
XFAIL MDAnalysisTests/coordinates/test_memory.py::TestMemoryReader::test_timeseries_values[slice0] - reason: MemoryReader uses deprecated stop inclusive indexing, see Issue #3893
XFAIL MDAnalysisTests/coordinates/test_memory.py::TestMemoryReader::test_timeseries_values[slice1] - reason: MemoryReader uses deprecated stop inclusive indexing, see Issue #3893
XFAIL MDAnalysisTests/coordinates/test_memory.py::TestMemoryReader::test_timeseries_values[slice2] - reason: MemoryReader uses deprecated stop inclusive indexing, see Issue #3893
XFAIL MDAnalysisTests/core/test_topologyattrs.py::TestResids::test_set_atoms
XFAIL MDAnalysisTests/lib/test_util.py::test_which - util.which does not get right binary on Windows
XFAIL MDAnalysisTests/converters/test_rdkit.py::TestRDKitFunctions::test_order_independant_issue_3339[C-[N+]#N] - Not currently tackled by the RDKitConverter
XFAIL MDAnalysisTests/converters/test_rdkit.py::TestRDKitFunctions::test_order_independant_issue_3339[C-N=[N+]=[N-]] - Not currently tackled by the RDKitConverter
XFAIL MDAnalysisTests/converters/test_rdkit.py::TestRDKitFunctions::test_order_independant_issue_3339[C-[O+]=C] - Not currently tackled by the RDKitConverter
XFAIL MDAnalysisTests/converters/test_rdkit.py::TestRDKitFunctions::test_order_independant_issue_3339[C-[N+]#[C-]] - Not currently tackled by the RDKitConverter
XFAIL MDAnalysisTests/coordinates/test_dcd.py::TestDCDReader::test_frame_collect_all_same - reason: DCDReader allows independent coordinates.This behaviour is deprecated and will be changedin 3.

[orbeckst]

In principle, tests should pass everywhere.

The Azure tests time out in the test

_________________________ Test_Fetch_Pdb.test_timeout _________________________

which looks like something that you added. I haven't looked at your code but it might simply be the case that some stuff needs to be written differently for windows.