Vertical Space in lists - different spaces before and after list

Question

Here at Stackexchange there are some questions related to vertical space in lists. For example: \topsep, \itemsep, \partopsep and \parsep - what does each of them mean (and what about the bottom)? How to remove the whitespace BEFORE itemize/enumerate?

My question just goes a little bit further:

I'd like to modify the whitespace BEFORE the list WITHOUT modifying the space AFTER the list. If i just change the parameter \topsep, both whitespaces will change. Ideally i want to change the parameters globally.

The only solution i found, is to include a negative vertical space before each list.

Answer 1

Her is a simple solution with enumitem:

\documentclass{report}
\usepackage{enumitem}
\setlist[enumerate, 1]{before={\addtolength{\topsep}{1cm}}, after=\vspace*{-1cm}}

\begin{document}

Some text. Some text.Some text. Some text. Some text. Some text.Some text. Some text. Some text. Some text.Some text. Some text. Some text. Some text.Some text. Some text.
    \begin{enumerate}
      \item First item \the\topsep
      \item Second item
      \item Third item
    \end{enumerate}
Some more text. Some more text. Some more text. Some more text. Some more text. Some more text. Some more text. Some more text.

\end{document}