Running Python code in Vim

How about adding an autocmd to your ~/.vimrc-file, creating a mapping:

autocmd FileType python map <buffer> <F9> :w<CR>:exec '!python3' shellescape(@%, 1)<CR>
autocmd FileType python imap <buffer> <F9> <esc>:w<CR>:exec '!python3' shellescape(@%, 1)<CR>

then you could press <F9> to execute the current buffer with python

Explanation:

• autocmd: command that Vim will execute automatically on {event} (here: if you open a python file)
• [i]map: creates a keyboard shortcut to <F9> in insert/normal mode
• <buffer>: If multiple buffers/files are open: just use the active one
• <esc>: leaving insert mode
• :w<CR>: saves your file
• !: runs the following command in your shell (try :!ls)
• %: is replaced by the filename of your active buffer. But since it can contain things like whitespace and other “bad” stuff it is better practise not to write :python %, but use:
• shellescape: escape the special characters. The 1 means with a backslash

TL;DR: The first line will work in normal mode and once you press <F9> it first saves your file and then run the file with python.
The second does the same thing, but leaves insert mode first