Can I change the dot to a colon after Proof in amsthm?

Question

I want to write Proof: in front of a proof instead of Proof. How may I achieve this?

Here is a MWE for the set up I have now:

\documentclass{article}
\usepackage{amsthm}
\begin{document}
\begin{proof}
\end{proof}
\end{document}

Answer 1

amsthm uses \@addpunct{.} to put the period. You can patch the \proof using xpatch to replace dot by :

\documentclass{article}
\usepackage{amsthm}
\usepackage{xpatch}
\makeatletter
\xpatchcmd{\proof}{\@addpunct{.}}{\@addpunct{:}}{}{}
\makeatother
\begin{document}
\begin{proof}
\end{proof}
\end{document}

If you want upright : use this:

\makeatletter
\xpatchcmd{\proof}{\@addpunct{.}}{\normalfont\,\@addpunct{:}}{}{}
\makeatother

Answer 2

Why not use \nopunct? This is the official way to do this.

\documentclass{article}
\usepackage{amsthm}
\begin{document}
\begin{proof}[Proof:\nopunct]
\end{proof}
\end{document}

Answer 3

From page 11 of the documentation. You can use

\documentclass[a4paper,12pt]{article}
\usepackage{amsmath,amsthm}
\makeatletter
\renewenvironment{proof}[1][\proofname]{\par
\pushQED{\qed}%
\normalfont \topsep6\p@\@plus6\p@\relax
\trivlist
\item\relax
{\itshape
#1\@addpunct{:}}\hspace\labelsep\ignorespaces
}{%
\popQED\endtrivlist\@endpefalse
}
\makeatother
\begin{document}
\begin{proof}
Here comes the proof.
\end{proof}
\end{document}