diff --git a/sgkit/tests/io/vcf/test_vcf_writer_utils.py b/sgkit/tests/io/vcf/test_vcf_writer_utils.py
index f9459ebe..1b566491 100644
--- a/sgkit/tests/io/vcf/test_vcf_writer_utils.py
+++ b/sgkit/tests/io/vcf/test_vcf_writer_utils.py
@@ -490,5 +490,5 @@ def test_interleave_speed():
 
     end = time.time()
     print(f"bytes written: {bytes_written}")
-    print(f"duration: {end-start}")
-    print(f"speed: {bytes_written/(1000000*(end-start))} MB/s")
+    print(f"duration: {end - start}")
+    print(f"speed: {bytes_written / (1000000 * (end - start))} MB/s")
diff --git a/sgkit/tests/test_stats_utils.py b/sgkit/tests/test_stats_utils.py
index 965a350a..d26b10cc 100644
--- a/sgkit/tests/test_stats_utils.py
+++ b/sgkit/tests/test_stats_utils.py
@@ -107,7 +107,7 @@ def sample_dataset(draw):
     # Split first dimension assignment into two groups and assign second
     # dimension with unique names since n cols will differ
     dims = [
-        (f"dim-0-{i%2}",) if i < n_1d else (f"dim-0-{i%2}", f"dim-1-{i}")
+        (f"dim-0-{i % 2}",) if i < n_1d else (f"dim-0-{i % 2}", f"dim-1-{i}")
         for i in range(n_arrs)
     ]
 
diff --git a/validation/gwas/method/regenie/hail_sim.py b/validation/gwas/method/regenie/hail_sim.py
index 181825a8..0c8c5bd4 100755
--- a/validation/gwas/method/regenie/hail_sim.py
+++ b/validation/gwas/method/regenie/hail_sim.py
@@ -49,8 +49,8 @@ def get_plink_sim_dataset(n_variants=16, n_samples=4, n_contigs=2, seed=0):
         for s in range(n_samples):
             data.append(
                 {
-                    "v": f"{c+1}:{v+1}:A:C",
-                    "s": f"S{s+1:07d}",
+                    "v": f"{c + 1}:{v + 1}:A:C",
+                    "s": f"S{s + 1:07d}",
                     "cm": 0.1,
                     "GT": hl.Call([rs.randint(0, 2), rs.randint(0, 2)]),
                 }