Add url_getsize() function (ultralytics#9247)

* Add `url_getsize()` function

Signed-off-by: Glenn Jocher <glenn.jocher@ultralytics.com>

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Update downloads.py

Signed-off-by: Glenn Jocher <glenn.jocher@ultralytics.com>

Signed-off-by: Glenn Jocher <glenn.jocher@ultralytics.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

utils/downloads.py

@@ -33,6 +33,12 @@ def gsutil_getsize(url=''):
     return eval(s.split(' ')[0]) if len(s) else 0  # bytes
 
 
+def url_getsize(url='https://ultralytics.com/images/bus.jpg'):
+    # Return downloadable file size in bytes
+    response = requests.head(url, allow_redirects=True)
+    return int(response.headers.get('content-length', -1))
+
+
 def safe_download(file, url, url2=None, min_bytes=1E0, error_msg=''):
     # Attempts to download file from url or url2, checks and removes incomplete downloads < min_bytes
     from utils.general import LOGGER