Get some information about the mappings you currently have active in Vim

map_info.vim

function! s:get_maps() abort
    return split(execute('map'), "\n")
endfunction

function! s:get_dict(mapping) abort
    let map_split = split(a:mapping, ' ')
    let l:mode = map_split[0]
    let l:map = map_split[2]
    return maparg(l:map, l:mode, v:false, v:true)
endfunction

function! s:get_len_rhs(map_dict) abort
    return len(a:map_dict['rhs'])
endfunction

function! s:sum_maps() abort
    let l:all_maps = s:get_maps()
    let l:this_total = 0
    for this_map in l:all_maps
        let l:this_total += s:get_len_rhs(s:get_dict(this_map))
    endfor

    let l:info_dict = {
                \ 'total number of mappings': len(l:all_maps),
                \ 'total length of mappings': l:this_total,
                \ 'average length of mappings': l:this_total / len(l:all_maps),
                \ }

    return l:info_dict
endfunction

echo s:sum_maps()