Calculating with python and appending result to file or register

Question

I found this vim tip which allows you to evaluate a Python expression and displays the result in the command line. You just have to add

:command! -nargs=+ Calc :py print <args>
:py from math import *

to your .vimrc and then you can do e.g.

:Calc sum([x^2 for x in range(100)])

Which displays 4950in my command line, as if I had executed :echo 4950. This is convenient, but I would like to know how I can either append the result at the location of my cursor, or add it to a certain register.

Answer 1

function! CalcAndAppend(expr)
py << EOF
import vim
evaluated = eval(vim.eval("a:expr"))

vim.current.buffer.append(str(evaluated), vim.current.window.cursor[0])
EOF
endfunction

function! CalcAndAppendRegister(reg, expr)
py << EOF
import vim
evaluated = eval(vim.eval("a:expr"))
evalString = "'" + str(evaluated) + "'"
register = vim.eval("a:reg")

vim.command("let @%s=%s" % (register,evalString))
EOF
endfunction

command! -nargs=+ Calc call CalcAndAppend(<q-args>) 

command! -register -nargs=+ CalcReg call CalcAndAppendRegister("<reg>",<q-args>)

Usage:
:Calc 2+2
appends 4 to the current buffer on one line below after cursor
:CalcReg a sum[x^2 for x in range(100)] put 4950 to the register named a

Answer 2

That's what pyeval() is good for. The only (minor) inconvenience is that you have to quote the expression you want to evaluate:

let @a = pyeval('sum([x^2 for x in range(100)])')

It works for all data types, and you can do with it everything you can do with a Vim expression. For example:

echo pyeval('[x^2 for x in range(100)]')

Answer 3

I do the following:

I create somewhere a calculator.py file containing this.

 import sys                                                                  
 print eval(sys.argv[1]) 

Then in vim i can do the command:

read! python calculator.py "[x^2 for x in range(100)]" 

Answer 4

1. Open the great vim.

2. Enter insert mode and add a python3 statement inside your text file buffer:

   print(5*5)

3. Go to normal mode (ESC or CTRL+C)

4. Press !! making sure the cursor is above that line. Your command bar will be filled like:

   :.!

5. fill the rest of command with python

   :.!python

6. press enter end you line will be evaluated:

   25