Refactor collections and fstrings (#7821)

* Update torch_utils.py

* Additional code refactoring

* tuples to sets

* Cleanup

utils/dataloaders.py

@@ -57,9 +57,7 @@ def exif_size(img):
     s = img.size  # (width, height)
     try:
         rotation = dict(img._getexif().items())[orientation]
-        if rotation == 6:  # rotation 270
-            s = (s[1], s[0])
-        elif rotation == 8:  # rotation 90
+        if rotation in [6, 8]:  # rotation 270 or 90
             s = (s[1], s[0])
     except Exception:
         pass
@@ -156,7 +154,7 @@ class InfiniteDataLoader(dataloader.DataLoader):
         return len(self.batch_sampler.sampler)
 
     def __iter__(self):
-        for i in range(len(self)):
+        for _ in range(len(self)):
             yield next(self.iterator)
 
 
@@ -224,10 +222,9 @@ class LoadImages:
                 self.cap.release()
                 if self.count == self.nf:  # last video
                     raise StopIteration
-                else:
-                    path = self.files[self.count]
-                    self.new_video(path)
-                    ret_val, img0 = self.cap.read()
+                path = self.files[self.count]
+                self.new_video(path)
+                ret_val, img0 = self.cap.read()
 
             self.frame += 1
             s = f'video {self.count + 1}/{self.nf} ({self.frame}/{self.frames}) {path}: '
@@ -390,7 +387,7 @@ class LoadStreams:
 
 def img2label_paths(img_paths):
     # Define label paths as a function of image paths
-    sa, sb = os.sep + 'images' + os.sep, os.sep + 'labels' + os.sep  # /images/, /labels/ substrings
+    sa, sb = f'{os.sep}images{os.sep}', f'{os.sep}labels{os.sep}'  # /images/, /labels/ substrings
     return [sb.join(x.rsplit(sa, 1)).rsplit('.', 1)[0] + '.txt' for x in img_paths]
 
 
@@ -456,7 +453,7 @@ class LoadImagesAndLabels(Dataset):
 
         # Display cache
         nf, nm, ne, nc, n = cache.pop('results')  # found, missing, empty, corrupt, total
-        if exists and LOCAL_RANK in (-1, 0):
+        if exists and LOCAL_RANK in {-1, 0}:
             d = f"Scanning '{cache_path}' images and labels... {nf} found, {nm} missing, {ne} empty, {nc} corrupt"
             tqdm(None, desc=prefix + d, total=n, initial=n, bar_format=BAR_FORMAT)  # display cache results
             if cache['msgs']: