Implement default class names (#1592)

models/yolo.py

 import argparse
 import logging
-import math
 import sys
 from copy import deepcopy
 from pathlib import Path
 
-sys.path.append('./')  # to run '$ python *.py' files in subdirectories
-logger = logging.getLogger(__name__)
-
+import math
 import torch
 import torch.nn as nn
 
+sys.path.append('./')  # to run '$ python *.py' files in subdirectories
+logger = logging.getLogger(__name__)
+
 from models.common import Conv, Bottleneck, SPP, DWConv, Focus, BottleneckCSP, Concat, NMS, autoShape
 from models.experimental import MixConv2d, CrossConv, C3
 from utils.autoanchor import check_anchor_order
@@ -82,6 +82,7 @@ class Model(nn.Module):
             logger.info('Overriding model.yaml nc=%g with nc=%g' % (self.yaml['nc'], nc))
             self.yaml['nc'] = nc  # override yaml value
         self.model, self.save = parse_model(deepcopy(self.yaml), ch=[ch])  # model, savelist, ch_out
+        self.names = [str(i) for i in range(self.yaml['nc'])]  # default names
         # print([x.shape for x in self.forward(torch.zeros(1, ch, 64, 64))])
 
         # Build strides, anchors