\documentclass{article}
\usepackage[autolanguage,boldmath]{numprint}
\usepackage{textcomp}
\usepackage{color}
\let\toprule\hline
\let\midrule\hline
\let\bottomrule\hline
\textwidth=6in\relax
\begin{document}
\section{Basics}
\paragraph{Basics}
\numprint{-123456}; \numprint{\pm 123456}; \numprint{+-3,1415927e-3.1}
\paragraph{Text vs Math}
\numprint{123456.134e123} and $\numprint{123456.134e123}$
\paragraph{Exponents}
Pure exponents: \numprint{e43242}; \numprint{-e43242}; \numprint{+-e43242}.
\paragraph{Expansion}
\def\numberbefore{1234}%
\def\totalnumber{\numberbefore.5678}%
\numprint{\totalnumber}
\paragraph{Units}
\numprint[N/mm^2]{-123456}
\numprint[\textdegree]{360}
\paragraph{Counters and Lengths}
Page: \cntprint{page}
Lengths: 
$\lenprint{\textwidth}$,
$\lenprint[pt]{\textwidth}$,
$\lenprint[in]{\textwidth}$,
$\lenprint[bp]{\textwidth}$,
$\lenprint[mm]{\textwidth}$,
$\lenprint[cm]{\textwidth}$.
\section{Customization}
\paragraph{Four-digit case}
\numprint{1234} vs.~ {\npfourdigitnosep\numprint{1234}};
But : \numprint{12345} vs.~ {\npfourdigitnosep\numprint{12345}}.
\paragraph{Missing zero}
{\npnoaddmissingzero\numprint{.1234}} vs.~ {\npaddmissingzero\numprint{.1234}};
But : {\npnoaddmissingzero\numprint{1234}} vs.~ {\npaddmissingzero\numprint{1234}};
\paragraph{Adding pluses}
\numprint{1234} vs.~ {\npaddplus\numprint{1234}};
And : \numprint{1234e4} vs.~ {\npaddplusexponent\numprint{1234e4}};
% % Test is not so portable across versions of numprint
% \paragraph{Rounding numbers}
% {\npnoround
%  $\numprint{1.123}$; $\numprint{1.149}$;
%  $\numprint{1}$; $\numprint{9.999}$; $\numprint{-9.999}$}
% {\nprounddigits{2}
%  $\numprint{1.123}$; $\numprint{1.149}$;
%  $\numprint{1}$; $\numprint{9.999}$; $\numprint{-9.999}$ }
\paragraph{Padding}
{\nplpadding{6}%
 $\numprint{1234}$; $\numprint{-1234}$;
 $\numprint{12345678}$; $\numprint{1234.5678}$ --}
vs.~{\nplpadding[x]{6}%
 $\numprint{1234}$; $\numprint{-1234}$;
 $\numprint{12345678}$; $\numprint{1234.5678}$}
\paragraph{Replacing zeros}
\numprint{123.00000}
  vs.~{\npreplacenull{\mbox{---}} \numprint{123.00000}}
\paragraph{Units format}
\numprint[N/mm^2]{300}
vs. {\renewcommand*\npunitcommand[1]{\ensuremath{\color{blue}\mathrm{#1}}}
 \numprint[N/mm^2]{300}}
\paragraph{New units}
\npdefunit{myin}{\!''}{0.01383700013}
$\lenprint[in]{\textwidth}$ vs.~ $\lenprint[myin]{\textwidth}$
%
\paragraph{Fancier}
\numprint{-123456}; \numprint{3,1415927e-32}
% pdflatex error: undefined control sequence \ndecimalsign
%%%{\ndecimalsign
{\ensuremath{\cdot}\npthousandsep{,}\npproductsign{*}%
\numprint{-123456}; \numprint{3,1415927e-32}}
\section{Tabulars}
\begin{tabular}{n{5}{3}}
123.45\\
12345.678\\
\end{tabular}
\begin{tabular}{n{5}{3}|n{5}{3}}
123.45 & 12345.678\\
\end{tabular}
{\tabcolsep0mm\small
\begin{tabular}{|n{5}{3}|n[3]{5}{3}|n[3][1]{5}{3}|N{5}{3}|}
\hline
123.45e12& 123.45e12& 123.45e12 & 123.45e12 \\
12345.678e123& 12345.678e123& 12345.678e123& 12345.678e123 \\
\hline
\end{tabular}}
\begin{tabular}{n{2}{1}n{2}{1}n{2}{1}n[1]{2}{1}}
\toprule
{without braces}&
{with braces}&
{with braces and box}&
\multicolumn{1}{l}{with braces, exp, and box}
\\
\midrule
%   pdflatex error: char for exponent used more than once
%%%abc def 12,3e3 rt&
{error} &
{abc def } 12,3e3 { rt}&
{\npmakebox[abc def ][l]{abc def }} 12,3e3 { rt}&
{\npmakebox[abc def ][l]{abc def }} 12,3e3 { rt}
\\
more 45,1 txt&
{more } 45,1 { txt}&
{\npmakebox[abc def ][l]{more }} 45,1 { txt}&
{\npmakebox[abc def ][l]{more }} 45,1 { txt}
\\
\midrule
not blue 45,1 txt&
{\color{blue}blue } 45,1 { txt}&
{\color{blue}\npmakebox[abc def ][l]{blue }} 45,1 { txt}&
{\color{blue}\npmakebox[abc def ][l]{blue }} 45,1 { txt}
\\
\bottomrule
\end{tabular}
\begin{tabular}{lN{12}{3}n{12}{3}}
\toprule
normal:&
123456123456.123e12&
123456123456.123e12
\\
bold:&
{\fontseries{b}\selectfont} 123456123456.123e12&
%{\npboldmath} 123456123456.123e12
\\
bold extended:&
{\bfseries} 123456123456.123e12&
{\boldmath} 123456123456.123e12
\\
\bottomrule
\end{tabular}
\begin{tabular}{%
>{{before \npafternum{ after}}}n[2]{12}{3}%
>{{\nprounddigits{4}}}n{3}{4}%
>{{\color{blue}}}n{12}{3}}
\toprule
123456123456.123e12&
12.12345&
123456.23e1
\\
12345.123e12&
12.1&
14561234.562e12
\\
\bottomrule
\end{tabular}
\begin{tabular}{>{{\npunit{N/mm^2}}}n{5}{3}}
\toprule
12345.123\\
12.12\\
{\npunit{psi}} 234.4\\
4.3\\
\bottomrule
\end{tabular}
\end{document}