Perl and C/C++ have perl-support.vim and c.vim by Fritz Mehner http://www.vim.org/account/profile.php?user_id=169
that support a very convenient auto completion shortcut in visual mode (e.g \aw for While construct or \ai for if else construct).
Does anybody know if such a comprehensive scripts also exist for Python?
python.vim doesn't seem to suppor this kind of auto completion.
Autocompletion is automatic: it happens without you doing anything.
What you want is not "autocompletion" but it can be achieved with varying levels of usefulness in a multitude of ways: insert mode mappings, abbreviations or full blown snippet expansion plugins like snipmate (abandoned original, maintained fork) or ultisnips.
I recommend the later option. This is a snipmate snippet:
# For
snippet for
for ${1:item} in ${2:items}:
${3:code...}
When you type for<Tab>, the snippet is expanded to:
for [item] in items:
code...
item is highlighted, ready to be changed to whatever you want and further <Tab>s jump you to items and code...:
for foo in [items]:
code...
for foo in bar:
[code...]
for foo in bar:
print foo
This is by far the most flexible option.
