diff --git a/jcvi/formats/base.py b/jcvi/formats/base.py
index 8617a145..30450c4a 100644
--- a/jcvi/formats/base.py
+++ b/jcvi/formats/base.py
@@ -7,7 +7,7 @@
 import sys
 
 from collections import OrderedDict
-from itertools import groupby, islice, cycle
+from itertools import cycle, groupby, islice
 
 from Bio import SeqIO
 from ..apps.base import (
@@ -337,7 +337,13 @@ def timestamp():
     return "{0}{1:02d}{2:02d}".format(dt.now().year, dt.now().month, dt.now().day)
 
 
-def must_open(filename, mode="r", checkexists=False, skipcheck=False, oappend=False):
+def must_open(
+    filename: str,
+    mode: str = "r",
+    checkexists: bool = False,
+    skipcheck: bool = False,
+    oappend: bool = False,
+):
     """
     Accepts filename and returns filehandle.
 
@@ -385,7 +391,7 @@ def must_open(filename, mode="r", checkexists=False, skipcheck=False, oappend=Fa
 
     elif filename.endswith(".bz2"):
         if "r" in mode:
-            cmd = "bzcat {0}".format(filename)
+            cmd = f"bzcat {filename}"
             fp = popen(cmd, debug=False)
         elif "w" in mode:
             import bz2
diff --git a/jcvi/formats/bed.py b/jcvi/formats/bed.py
index 330d8577..df6a2bb6 100755
--- a/jcvi/formats/bed.py
+++ b/jcvi/formats/bed.py
@@ -135,7 +135,7 @@ def gffline(self, type="match", source="default"):
                 score,
                 strand,
                 ".",
-                "ID=" + self.accn,
+                f"ID={self.accn}",
             )
         )
         return row
diff --git a/jcvi/graphics/landscape.py b/jcvi/graphics/landscape.py
index a53bc1b1..91be96ff 100644
--- a/jcvi/graphics/landscape.py
+++ b/jcvi/graphics/landscape.py
@@ -582,7 +582,7 @@ def linearray(binfile, chr, window, shift):
     m, n = zip(*mn)
 
     m = np.array(m, dtype="float")
-    w = window / shift
+    w = window // shift
     m = moving_sum(m, window=w)
     return m
 
@@ -883,7 +883,7 @@ def heatmap(args):
 
     owindow = clen / 100
     if owindow > window:
-        window = owindow / shift * shift
+        window = owindow // shift * shift
 
     stackplot(ax, stackbins, nbins, palette, chr, window, shift)
     ax.text(
@@ -958,7 +958,7 @@ def draw_gauge(ax, margin, maxl, rightmargin=None):
     ax.plot([margin, 1 - rightmargin], [1 - margin, 1 - margin], "k-", lw=2)
 
     best_stride = autoscale(maxl)
-    nintervals = maxl * 1.0 / best_stride
+    nintervals = maxl / best_stride
 
     xx, yy = margin, 1 - margin
     tip = 0.005