Naming a Graph (Graph Theory)

Question

\begin{tikzpicture}
[acteur/.style={circle, fill=black,thick, inner sep=4pt, minimum size=0.2cm}]
\node (A) at (5,12) [acteur][label=right:0]{};
\node (B) at (8,11) [acteur][label=right:1]{};
\node (C) at (9,9) [acteur][label=left:2]{};
\node (D) at (8,7) [acteur][label=right:3]{};
\node (E) at (5,6) [acteur][label=below:4]{};
\node (F) at (2,7) [acteur][label=right:5]{};
\node (G) at (1,9) [acteur][label=left:6]{};
\node (H) at (2,11) [acteur][label=right:7]{};
\path (A) edge [loop above, thick] node {} (0);
\path (B) edge [loop above, thick] node {} (1);
\path (C) edge [loop above, thick] node {} (2);
\path (D) edge [loop above, thick] node {} (3);
\path (E) edge [loop above, thick] node {} (4);
\path (F) edge [loop above, thick] node {} (5);
\path (G) edge [loop above, thick] node {} (6);
\path (H) edge [loop above, thick] node {} (7);
\end{tikzpicture}

It occur an error when I change

label 0 to label (0,0,0), label 1 to label<br/> (0,0,1) ... and so on

like this

\node (A) at (5,12) [acteur][label=right:(0,0,0)]{};
\node (B) at (8,11) [acteur][label=right:(0,0,1)]{};
... and so on

Answer 1

Welcome to TeX.SE! If you place some sensitive character like (, it might be misinterpreted by the parser. In almost all situations putting things in groups, i.e. putting { and } around them, fixes the issue. And you can make your code much shorter using \foreach. (In principle, one \foreach loop is sufficient, but for the sake of the argument I am using two here.)

\documentclass[tikz,border=3.14mm]{standalone}
\begin{document}
\begin{tikzpicture}[acteur/.style={circle, fill=black,thick, inner sep=4pt, minimum size=0.2cm}] 
\foreach \X [count=\Y starting from 0,evaluate=\Y as \Z using {90-\Y*45}] in {A,...,H}
{\node (\X) at (\Z:3) [acteur][label=right:{(0,0,\Y)}]{};}
\foreach \X [count=\Y starting from 0] in {A,...,H}
{\path (\X) edge [loop above, thick] (\Y);}
\end{tikzpicture}
\end{document}