I discovered this trick while trying to do some quick investigation in Vim, and not wanting to have to leave the editor, found a way to quickly replace Python code (or anything you can pipe to an external command) with it's output in Vim. What you do is, write the code inside a buffer, then select it in visual mode. Once it's selected, press : and you will get Vim's :'<,'> range, which means all the text between the beginning and end of the visual cursor.

Single Lines

Say, for example I want to do some checking on where the position of a particular character is in a string. I could do this:

print([i for i, c in enumerate('ABCDQQFGHQQIQJ') if c == 'Q'])

Then select the line it's on by pressing V, then press : and execute :'<,'>!python and it will be replaced with [4, 5, 9, 10, 12] inline.

Multiline

It's also useful for multiline things, such as using requests to pull a webpage into your buffer.

import requests
print(requests.get("http://api.ipify.org").text)

Select both lines with V, then execute them and the code will be replaced by your external IP address.

You can pretty much do this trick with any standard-output-writing program. So, you could do it with shell scripts, lua, node, php anything you want.

SQL Queries

I just realized while writing this how cool it is to write a query and have it replaced by the data:

SELECT * FROM lottery_drawings LIMIT 5;

executed with :'<,'>!sqlite3 -header /Users/adam/code/lottery_data.sqlite3 becomes:

date|numbers|hash|lottery_name
2015-10-15 00:00:00|38-7-42-15-18 9|4f33b4f41656d17cc4707ad52245cf0d|Lucky For Life
2015-10-12 00:00:00|7-37-43-48-4 5|918dcc8d28314189c52d85c899812e86|Lucky For Life
2015-10-08 00:00:00|8-21-48-42-1 4|1c804ff089ed12ecd6eab4f8ad9e39f0|Lucky For Life
2015-10-05 00:00:00|48-28-41-31-8 5|fb3c0624dbca146a24b4103ee227f10a|Lucky For Life
2015-10-01 00:00:00|33-4-41-46-24 4|9714ff834aaa654c019ff0ad0607a4dc|Lucky For Life

Binding

If you're going to use this a lot, you might think about rebinding a key in visual mode to do your most common operation. Just place this line in your vimrc, replacing 'python' with the command you want to execute, and with the keybind you want to use.

vnoremap <F5> :!python<CR>