Update signature style for optional arguments, part 3.
diff --git a/Doc/library/codeop.rst b/Doc/library/codeop.rst
index e4523b6..2c066ef 100644
--- a/Doc/library/codeop.rst
+++ b/Doc/library/codeop.rst
@@ -26,7 +26,7 @@
To do just the former:
-.. function:: compile_command(source[, filename[, symbol]])
+.. function:: compile_command(source, filename="<input>", symbol="single")
Tries to compile *source*, which should be a string of Python code and return a
code object if *source* is valid Python code. In that case, the filename