diff --git a/source/c01/c01_31.md b/source/c01/c01_31.md
index 1864dab..e5e8abd 100644
--- a/source/c01/c01_31.md
+++ b/source/c01/c01_31.md
@@ -61,8 +61,8 @@ hello world
 >>> msg='hello----world'
 >>> msg.split('-')
 ['hello', '', '', '', 'world']
->>> 
->>> filter(lambda item: True if item else False, msg.split('-'))
+>>>
+>>> filter(bool, msg.split('-'))
 ['hello', 'world']
 ```
 
diff --git a/source/c01/c01_31.rst b/source/c01/c01_31.rst
index e235e95..22ef18e 100644
--- a/source/c01/c01_31.rst
+++ b/source/c01/c01_31.rst
@@ -69,8 +69,8 @@
    >>> msg='hello----world'
    >>> msg.split('-')
    ['hello', '', '', '', 'world']
-   >>> 
-   >>> filter(lambda item: True if item else False, msg.split('-'))
+   >>>
+   >>> filter(bool, msg.split('-'))
    ['hello', 'world']
 
 |image2|