Split out IO logic from high level functions (#392)

[jstockwin]

Pull request

Adds two new functions (extract_text_from_io and extract_pages_from_io) to high_level.py, allowing you to call extract_text and extract_pages without having the file locally.

Closes #392

Notes

• I've created the new functions, *_from_io to avoid breaking changes to the original functions. This is not very consistent with the extract_text_to_fp at the top of the file, perhaps. Happy to implement alternatives.
• I've used inf as the new IO parameter, even though I don't really like the name. This is to be consistent with extract_text_to_fp. Other places in the code use fp. Happy to change.
• I added the test in a new file, as the existing code has test_highlevel_extracttext.py. Is this correct, or should this all be in one test_high_level.py?

How Has This Been Tested?

I've added tests for extract_text_from_io, but couldn't find any existing tests for extract_pages?

Checklist

• I have added tests that prove my fix is effective or that my feature
  works
• I have added docstrings to newly created methods and classes
• I have optimized the code at least one time after creating the initial
  version
• I have updated the README.md or I am verified that this
  is not necessary (not necessary)
• I have updated the readthedocs documentation or I
  verified that this is not necessary (not necessary as the read the docs page on this is auto generated from docstrings)
• I have added a consice human-readable description of the change to
  CHANGELOG.md

[pietermarsman]

I thought you were going to do something like this read_csv() method in pandas. You can pass a path or a file-like object. So the user does not need to learn a new method if (s)he wants the same functionality.

[jstockwin]

@pietermarsman PR updated to keep the same function name and simply allow either a string or a file-like object. I've added an open_filename context manager to help do this. I was tempted to put this in utils, but it didn't quite seem to fit...

I've essentially followed advice from here about how to do this... https://stackoverflow.com/questions/7268353/how-to-accept-both-filenames-and-file-like-objects-in-python-functions

[pietermarsman]

Looks perfect!

I suggested 2 minor changes.

[jstockwin]

@pietermarsman thanks. I've updated the first commit to resolve contributing being out of date, and added a new commit moving the open_filename to utils.

Please take another look when you get chance.

[pietermarsman]

😄