* fix isascii for python3.6

* update comment with python 3.7 note
Co-authored-by: Glenn Jocher <glenn.jocher@ultralytics.com>

* Update relative `ROOT` logic

* python 3.9 Path().is_relative_to() removal

* Allow YOLOv5 execution from arbitrary `cwd`

* Fix str bugs

* Automatic Chinese fonts plotting

* Default PIL=False

`check_file()` is now limited to searching opt-in directories: /data, /models, /utils. This prevents large non-project directories like /.git and /venv from being searched, which may cause `check_file()` to slow significantly.

* Validate best.pt on train end

* 0.7 iou for COCO only

* pass callbacks

* active model.float() if not half

* print Validating best.pt...

* add newline

Add badge with link to join the new YOLOv5 Slack Forum!
https://join.slack.com/t/ultralytics/shared_invite/zt-w29ei8bp-jczz7QYUmDtgo6r6KcMIAg

* Fix `root` referenced before assignment

Fix for bug introduced by #4919 discovered on VOC autodownload:
```
python train.py --data VOC.yaml
```

* Cleanup

* Replace `os.system('unzip file.zip')` -> `ZipFile.extractall()`

* Cleanup

* Add arguments to TensorFlow NMS call

* Add regex substitution to reorder Identity_*

* Delete reorder in docstring

* Cleanup

* Cleanup2

* Removed `+ \` on string ends (not needed)
Co-authored-by: Glenn Jocher <glenn.jocher@ultralytics.com>

* Avoid out-of-image class labels

* Update plots.py

* Cleanup
Co-authored-by: Glenn Jocher <glenn.jocher@ultralytics.com>

* evolve fix

* Enable login timeout

* fix pkg

* check rank

* don't relogin

* fix

* reformat

* evolve fix

* Enable login timeout

* fix pkg

* check rank

* don't relogin

* Annotator `check_font()` RANK -1 remove progress

* Cleanup

* Simplify `check_requirements()` usage

* remove assert, print()

* Update `sys.path.append(str(ROOT))`

* Cleanup

* Refactor argparser printing to `print_args()`

* Cleanup

* evolve fix

* Enable login timeout

* fix pkg

Defines dataset labels *.cache version in a single place, fixing a bug introduced in #4845.

PR should produce datasets sorted alphabetically by filename. Cache version incremented to 0.5. 

Note: will force a one-time re-caching of existing datasets on first-use.

* Unpin Pillow

* Update requirements.txt

* Update plots.py

* Fix val.py study plot

* call plot_val_study

* Rename plot_study_txt to plot_val_study

* Add fused conv support

* Set all saved_model values to non trainable

* Fix TFLite fp16 model export

* Fix int8 TFLite conversion

Follows #4823

* added callbacks

* added back callback to main

* added save_dir to callback output

* merged in upstream

* removed ghost code

* added url check

* Add url2file()

* Update file-only
Co-authored-by: Glenn Jocher <glenn.jocher@ultralytics.com>

Also disable `/weights` dir creation when evolving as no weights are saved and empty folder causes user expectations of weights.