Lazy load requests dependency

[BeyondEvil]

Closed PR (and start of discussion): https://github.com/pytest-dev/pytest-base-url/pull/9

Before I consider implementing the lazy load, I need to understand the time/speed issue 100% and have exhausted all other (resonable) approaches.

@boxed

[RonnyPfannschmidt]

i just took a look, from my pov #9 is a solid solution that changes the import time to a point that reduces cost, i don't think there is another reasonable approach to avoid that import when its not needed

[boxed]

There's an extremely tiny performance hit on doing an import inside a function, as every time you enter the function the import actually runs and basically checks a dict if the module is present and then bails out.

This performance difference doesn't seem to be relevant as it relates to this ticket as the _verify_url function is only called once per session, so it's the exact same as if it was in the top of the file.

Now, if you just have the plugin installed in the virtualenv, pytest will load it, causing the import to be hit if it's on the top level. This costs ~200ms.

Here's a little demonstration of what I'm talking about:

 ◰² venv  ~/P/scientist    virtualenv -p (which python3) venv                                303ms  Tue May 19 11:31:15 2020
Running virtualenv with interpreter /usr/local/bin/python3
Using base prefix '/usr/local/Cellar/python/3.7.7/Frameworks/Python.framework/Versions/3.7'
New python executable in /Users/andersh/Projects/scientist/venv/bin/python3.7
Also creating executable in /Users/andersh/Projects/scientist/venv/bin/python
Installing setuptools, pip, wheel...
sourcedone.
 ◰³ venv  ~/P/scientist    source venv/bin/activate.fish                                     17.5s  Tue May 19 11:31:36 2020
 ◰³ venv  ~/P/scientist    pip install hammett                                                       Tue May 19 11:32:19 2020
Processing /Users/andersh/Library/Caches/pip/wheels/39/88/68/060e6095f2d869855bfcb8ba17cd88828cfb8fe4ef954c7a20/hammett-0.6.0-cp37-none-any.whl
Collecting astunparse
  Using cached astunparse-1.6.3-py2.py3-none-any.whl (12 kB)
Collecting colorama
  Using cached colorama-0.4.3-py2.py3-none-any.whl (15 kB)
Requirement already satisfied: wheel<1.0,>=0.23.0 in ./venv/lib/python3.7/site-packages (from astunparse->hammett) (0.34.2)
Collecting six<2.0,>=1.6.1
  Using cached six-1.14.0-py2.py3-none-any.whl (10 kB)
Installing collected packages: six, astunparse, colorama, hammett
Successfully installed astunparse-1.6.3 colorama-0.4.3 hammett-0.6.0 six-1.14.0
 ◰³ venv  ~/P/scientist    python -m hammett                                                1754ms  Tue May 19 11:32:31 2020
.......
7 succeeded, 0 failed, 0 skipped
 ◰³ venv  ~/P/scientist    python -m pytest                                                  101ms  Tue May 19 11:32:33 2020
/Users/andersh/Projects/scientist/venv/bin/python: No module named pytest
 !  ◰³ venv  ~/P/scientist    pip install pytest                                                    Tue May 19 11:32:40 2020
Collecting pytest
  Using cached pytest-5.4.2-py3-none-any.whl (247 kB)
Collecting packaging
  Downloading packaging-20.4-py2.py3-none-any.whl (37 kB)
Collecting wcwidth
  Using cached wcwidth-0.1.9-py2.py3-none-any.whl (19 kB)
Collecting attrs>=17.4.0
  Using cached attrs-19.3.0-py2.py3-none-any.whl (39 kB)
Collecting py>=1.5.0
  Using cached py-1.8.1-py2.py3-none-any.whl (83 kB)
Collecting importlib-metadata>=0.12; python_version < "3.8"
  Using cached importlib_metadata-1.6.0-py2.py3-none-any.whl (30 kB)
Collecting more-itertools>=4.0.0
  Using cached more_itertools-8.3.0-py3-none-any.whl (44 kB)
Collecting pluggy<1.0,>=0.12
  Using cached pluggy-0.13.1-py2.py3-none-any.whl (18 kB)
Collecting pyparsing>=2.0.2
  Using cached pyparsing-2.4.7-py2.py3-none-any.whl (67 kB)
Requirement already satisfied: six in ./venv/lib/python3.7/site-packages (from packaging->pytest) (1.14.0)
Collecting zipp>=0.5
  Using cached zipp-3.1.0-py3-none-any.whl (4.9 kB)
Installing collected packages: pyparsing, packaging, wcwidth, attrs, py, zipp, importlib-metadata, more-itertools, pluggy, pytest
Successfully installed attrs-19.3.0 importlib-metadata-1.6.0 more-itertools-8.3.0 packaging-20.4 pluggy-0.13.1 py-1.8.1 pyparsing-2.4.7 pytest-5.4.2 wcwidth-0.1.9 zipp-3.1.0
 ◰³ venv  ~/P/scientist    python -m pytest                                                 4448ms  Tue May 19 11:32:49 2020
====================================================== test session starts ======================================================
platform darwin -- Python 3.7.7, pytest-5.4.2, py-1.8.1, pluggy-0.13.1
rootdir: /Users/andersh/Projects/scientist
collected 7 items                                                                                                               

tests/test_scientist.py .......                                                                                           [100%]

======================================================= 7 passed in 0.06s =======================================================
 ◰³ venv  ~/P/scientist    pip install pytest-base-url                                       356ms  Tue May 19 11:32:51 2020
Collecting pytest-base-url
  Downloading pytest_base_url-1.4.1-py2.py3-none-any.whl (7.1 kB)
Collecting requests>=2.9
  Downloading requests-2.23.0-py2.py3-none-any.whl (58 kB)
     |████████████████████████████████| 58 kB 3.7 MB/s 
Requirement already satisfied: pytest>=2.7.3 in ./venv/lib/python3.7/site-packages (from pytest-base-url) (5.4.2)
Collecting certifi>=2017.4.17
  Downloading certifi-2020.4.5.1-py2.py3-none-any.whl (157 kB)
     |████████████████████████████████| 157 kB 8.6 MB/s 
Collecting chardet<4,>=3.0.2
  Downloading chardet-3.0.4-py2.py3-none-any.whl (133 kB)
     |████████████████████████████████| 133 kB 9.4 MB/s 
Collecting idna<3,>=2.5
  Downloading idna-2.9-py2.py3-none-any.whl (58 kB)
     |████████████████████████████████| 58 kB 11.2 MB/s 
Collecting urllib3!=1.25.0,!=1.25.1,<1.26,>=1.21.1
  Downloading urllib3-1.25.9-py2.py3-none-any.whl (126 kB)
     |████████████████████████████████| 126 kB 8.0 MB/s 
Requirement already satisfied: wcwidth in ./venv/lib/python3.7/site-packages (from pytest>=2.7.3->pytest-base-url) (0.1.9)
Requirement already satisfied: pluggy<1.0,>=0.12 in ./venv/lib/python3.7/site-packages (from pytest>=2.7.3->pytest-base-url) (0.13.1)
Requirement already satisfied: packaging in ./venv/lib/python3.7/site-packages (from pytest>=2.7.3->pytest-base-url) (20.4)
Requirement already satisfied: py>=1.5.0 in ./venv/lib/python3.7/site-packages (from pytest>=2.7.3->pytest-base-url) (1.8.1)
Requirement already satisfied: importlib-metadata>=0.12; python_version < "3.8" in ./venv/lib/python3.7/site-packages (from pytest>=2.7.3->pytest-base-url) (1.6.0)
Requirement already satisfied: attrs>=17.4.0 in ./venv/lib/python3.7/site-packages (from pytest>=2.7.3->pytest-base-url) (19.3.0)
Requirement already satisfied: more-itertools>=4.0.0 in ./venv/lib/python3.7/site-packages (from pytest>=2.7.3->pytest-base-url) (8.3.0)
Requirement already satisfied: pyparsing>=2.0.2 in ./venv/lib/python3.7/site-packages (from packaging->pytest>=2.7.3->pytest-base-url) (2.4.7)
Requirement already satisfied: six in ./venv/lib/python3.7/site-packages (from packaging->pytest>=2.7.3->pytest-base-url) (1.14.0)
Requirement already satisfied: zipp>=0.5 in ./venv/lib/python3.7/site-packages (from importlib-metadata>=0.12; python_version < "3.8"->pytest>=2.7.3->pytest-base-url) (3.1.0)
Installing collected packages: certifi, chardet, idna, urllib3, requests, pytest-base-url
Successfully installed certifi-2020.4.5.1 chardet-3.0.4 idna-2.9 pytest-base-url-1.4.1 requests-2.23.0 urllib3-1.25.9
 ◰³ venv  ~/P/scientist    python -m pytest                                                 2703ms  Tue May 19 11:33:03 2020
====================================================== test session starts ======================================================
platform darwin -- Python 3.7.7, pytest-5.4.2, py-1.8.1, pluggy-0.13.1
rootdir: /Users/andersh/Projects/scientist
plugins: base-url-1.4.1
collected 7 items                                                                                                               

tests/test_scientist.py .......                                                                                           [100%]

======================================================= 7 passed in 0.08s =======================================================
 ◰³ venv  ~/P/scientist                                                                      450ms  Tue May 19 11:33:05 2020```

[boxed]

If I sound frustrated, I do apologize! I am having this long discussion with many people and if I fail to convince just one person then all my work is for nothing. It's not an ideal situation! :)

[nicoddemus]

I concur with @RonnyPfannschmidt... I think plugins are recommended to avoid costly high-level imports, specially if they might not be used in runtime at all for all tests or even for a few tests, and seems the case for pytest-base-url which is activated by an option.

So 👍 from me. 😁

[BeyondEvil]

Looks like we're lazy loading the requests lib. @boxed 😂

[boxed]

Fantastic! And if you have other similar projects, do keep an eye out for similar things. We're all in this together.

[boxed]

Sooo..... do you reopen the PR?

[BeyondEvil]

Sooo..... do you reopen the PR?

NEJ!

[BeyondEvil]

🤷‍♂️

[boxed]

Eh... well that's weird. Ok, well, the diff is really trivial anyway. I don't care about attribution in the git log.