Proposed tip Please edit this page to improve it, or add your comments below (do not use the discussion page).
I was using the Python omni-completion feature in Vim, and I noticed that when you complete a module name, it inserts the module name, followed by a dot (presumably because you would then want to access something inside the module). This is helpful, except that it breaks common omnicompletion keybindings, such as
imap <silent> <buffer> . .<C-X><C-O>
In order to get completions for this module, one would have to either manually type <C-X><C-O> to run the completion function again, or delete and then re-insert the period. The correct solution is, of course, to fix the Python omnicompletion module. However, this 'feature' is present in all default installations of Vim.
Here is a stopgap solution. On <CR>, it accepts the current completion, and then runs a <C-R>= expression that checks to see if the character before the cursor is a '.'. If it is, then it runs omnicomplete again. The tricky bit about this is that it needs to accept the completion before it can check the cursor positsion, or else it will be checking against the partially completed text. The col('.')-1 check avoids a problem where you return without a selected match which lands you at column 1 of the next line.
imap <silent> <expr> <buffer> <CR> pumvisible() ? "<CR><C-R>=(col('.')-1&&match(getline(line('.')), '\\.',
\ col('.')-2) == col('.')-2)?\"\<lt>C-X>\<lt>C-O>\":\"\"<CR>"
\ : "<CR>"