diff --git a/pymbolic/interop/maxima.py b/pymbolic/interop/maxima.py
index 4be1dcf92e00769c6aa33b446e91e9488c346c91..cfe3397593ed569a5a846dbe9ef3f31afbb40631 100644
--- a/pymbolic/interop/maxima.py
+++ b/pymbolic/interop/maxima.py
@@ -381,9 +381,9 @@ class MaximaKernel:
             import sys
             self.child.logfile = sys.stdout
 
-    def _sendline(self, l):
+    def _sendline(self, line):
         self._check_debug()
-        self.child.sendline(l)
+        self.child.sendline(line)
 
     def exec_str(self, s, enforce_prompt_numbering=True):
         cmd = s+";"
@@ -420,8 +420,8 @@ class MaximaKernel:
 
     def clean_eval_str_with_setup(self, setup_lines, s):
         self.reset()
-        for l in setup_lines:
-            self.exec_str(l)
+        for line in setup_lines:
+            self.exec_str(line)
 
         return self.eval_str(s)
 
diff --git a/pymbolic/mapper/graphviz.py b/pymbolic/mapper/graphviz.py
index 776dd67c86ce9987b7aa97323eb1d5bc3f6adc8c..f4746269b401f02ad82fd8e818c55faf78facd3c 100644
--- a/pymbolic/mapper/graphviz.py
+++ b/pymbolic/mapper/graphviz.py
@@ -46,7 +46,7 @@ class GraphvizMapper(WalkMapper):
         """Return the dot source code for a previously traversed expression."""
 
         return "digraph expression {\n%s\n}" % (
-            "\n".join("  "+l for l in self.lines))
+            "\n".join("  "+line for line in self.lines))
 
     def get_id(self, expr):
         "Generate a unique node ID for dot for *expr*"
diff --git a/pymbolic/primitives.py b/pymbolic/primitives.py
index 0ca0a6d5d898008ee65a1c078eff90c670c8f7de..ef67fb94a38ffcd7862d39e5b795a94e64123a0f 100644
--- a/pymbolic/primitives.py
+++ b/pymbolic/primitives.py
@@ -1467,7 +1467,7 @@ class Slice(Expression):
 
     @property
     def start(self):
-        if len(self.children) > 1:
+        if len(self.children) > 0:
             return self.children[0]
         else:
             return None