Better note that str.zfill() was added in 2.2.2 as well. ;-(

freddrake · freddrake · commit e55bec256664 · 2002-11-16T00:44:00.000Z
diff --git a/Doc/lib/libstdtypes.tex b/Doc/lib/libstdtypes.tex
@@ -723,6 +723,7 @@ \subsubsection{String Methods \label{string-methods}}
 Return the numeric string left filled with zeros in a string
 of length \var{width}. The original string is returned if
 \var{width} is less than \code{len(\var{s})}.
+\versionadded{2.2.2}
 \end{methoddesc}
 
 
