Update 01_notebook.md

guoci · web-flow · commit 9bb786bc9dc6 · 2019-03-11T12:18:53.000-04:00
diff --git a/chapter01_basic/01_notebook.md b/chapter01_basic/01_notebook.md
@@ -67,7 +67,7 @@ _ * 3
 my_notebook.ipynb
 ```
 
-On Windows, one may replaces `ls` by `dir`.
+On Windows, one may replace `ls` by `dir`.
 
 5. IPython comes with a library of **magic commands**. These commands are convenient shortcuts to common actions. They all start with `%` (the percent character). We can get the list of all magic commands with `%lsmagic`:
 
