Inspirated

\documentclass{beamer}
 
\setbeamercovered{transparent}
 
\usepackage{pxfonts}
\usepackage{listings}
 
\begin{document}
 
\lstset{language=python,
        numbers=left,
        numberstyle=\tiny,
        showstringspaces=false,
        aboveskip=-40pt,
        frame=leftline
        }
 
\begin{frame}[fragile]
\frametitle{\texttt{parrot.py}}
\begin{semiverbatim}
\pause
\begin{lstlisting}
if __name__ == "__main":
 
\end{lstlisting}
 
\pause
\begin{lstlisting}[firstnumber=last]
    print "Oh yes, the, uh,
           the Norwegian Blue..."
    print "What's, uh...
           What's wrong with it? "
 
\end{lstlisting}
 
\pause
\begin{lstlisting}[firstnumber=last]
    print "I'll tell you what's wrong with it,
           my lad."
    print "'E's dead,
           that's what's wrong with it!"
 
\end{lstlisting}
\end{semiverbatim}
\end{frame}
 
\end{document}