diff --git a/mmpose/datasets/pipelines/bottom_up_transform.py b/mmpose/datasets/pipelines/bottom_up_transform.py
index 2cec1be4d3..89e31a8397 100644
--- a/mmpose/datasets/pipelines/bottom_up_transform.py
+++ b/mmpose/datasets/pipelines/bottom_up_transform.py
@@ -165,8 +165,8 @@ def __call__(self, joints):
             tot = 0
             for idx, pt in enumerate(joints[i]):
                 x, y = int(pt[0]), int(pt[1])
-                if (pt[2] > 0 and x >= 0 and y >= 0 and x < self.output_res
-                        and y < self.output_res):
+                if (pt[2] > 0 and 0 <= y < self.output_res
+                        and 0 <= x < self.output_res):
                     if self.tag_per_joint:
                         visible_kpts[i][tot] = \
                             (idx * output_res**2 + y * output_res + x, 1)
diff --git a/mmpose/models/backbones/regnet.py b/mmpose/models/backbones/regnet.py
index 24825bcd41..f5fcf74de0 100644
--- a/mmpose/models/backbones/regnet.py
+++ b/mmpose/models/backbones/regnet.py
@@ -132,7 +132,7 @@ def __init__(self,
         self.stem_channels = stem_channels
         self.base_channels = base_channels
         self.num_stages = num_stages
-        assert num_stages >= 1 and num_stages <= 4
+        assert 1 <= num_stages <= 4
         self.strides = strides
         self.dilations = dilations
         assert len(strides) == len(dilations) == num_stages
diff --git a/mmpose/models/backbones/resnet.py b/mmpose/models/backbones/resnet.py
index 14f2e80cc1..f6a5bb74c6 100644
--- a/mmpose/models/backbones/resnet.py
+++ b/mmpose/models/backbones/resnet.py
@@ -500,7 +500,7 @@ def __init__(self,
         self.stem_channels = stem_channels
         self.base_channels = base_channels
         self.num_stages = num_stages
-        assert num_stages >= 1 and num_stages <= 4
+        assert 1 <= num_stages <= 4
         self.strides = strides
         self.dilations = dilations
         assert len(strides) == len(dilations) == num_stages