\ExplSyntaxOn
\newcommand{\pyval}[1]{%
	\str_case:nn{#1}{%
		{ 0 }{ m = \SI{-1.6911+-0.0000}{  }}
		{ 1 }{ p = \SI{567.6618+-0.0000}{  }}
		{ 2 }{ a = \SI{-621.1199+-0.0000}{  }}
		{ 3 }{ c = \SI{0.9318+-0.0000}{  }}
	}
}
\ExplSyntaxOff