pweave using results='tex' in chunk headers creates empty lines in the tex file

[steven-omaha]

Consider the following file input.texw:

\documentclass{standalone}
\begin{document}
<<results='tex', echo=False>>=
print(1)
@
\end{document}

Running pweave -f tex input.texw creates the following input.tex:

\documentclass{standalone}
\begin{document}


1

\end{document}

This creates problems when the user wants to print python-results inline in tex files. Example:

\documentclass{standalone}
\usepackage{siunitx}
\begin{document}
\SI{%
<<results='tex', echo=False>>=
print(1)
@
}{\meter}
\end{document}

This compiles to

\documentclass{standalone}
\usepackage{siunitx}
\begin{document}
\SI{%


1

}{\meter}
\end{document}

which cannot be processed by pdflatex input.tex:

Runaway argument?
{
! Paragraph ended before \SI  was complete.
<to be read again>
                   \par
l.5

!  ==> Fatal error occurred, no output PDF file produced!

The expected input.tex file would have been this:

\documentclass{standalone}
\usepackage{siunitx}
\begin{document}
\SI{%
1
}{\meter}
\end{document}