How to get returned value from python functions in vim scripts ?

[Lenin]

Hi,

I want to get returned value from python functions in vim scripts, how can I make it ?

Thanks

[Alec Tica]

Hi,

In ruby is something like:

VIM::command("return #{my_ruby_var.inspect}")

I expect to be the same in python.

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[Marcin Szamotulski]

Hi,

You can do

import vim

and then use

vim.command("let g:return="+str(value))

This works also with dictionaries and lists (though I've encountered that some
times singe quotes inside value when it is a dictionary or a list may couse
troubles). So I would like to know a better method.

Best,
Marcin

[Lenin]

Alec: It seems :py vim.command('return 1') will throw an error that says "return not inside a function".

Marcin: Yes, I am using vim variables to transfer values from python functions currently, but I think this method is ugly, I'd like to know a better solution.

Thank you both.

2011/6/6 Marcin Szamotulski <msz...@gmail.com>

[Ivan Krasilnikov]

On Tue, Jun 7, 2011 at 08:47, Lenin <leni...@gmail.com> wrote:
> Alec: It seems :py vim.command('return 1') will throw an error that says
> "return not inside a function".

It works fine if you call it inside a vim function:

:function Func()
: py vim.command('return 1')
:endfunction

[Marko Mahnič]

On Jun 7, 8:36 am, Ivan Krasilnikov <inf...@gmail.com> wrote:

> On Tue, Jun 7, 2011 at 08:47, Lenin <lenin....@gmail.com> wrote:
> > Alec: It seems :py vim.command('return 1') will throw an error that says
> > "return not inside a function".
>
> It works fine if you call it inside a vim function:
>
> :function Func()
> :  py vim.command('return 1')
> :endfunction

The script vimuiex (2606 on vim.org) uses callbacks to process the
returned values:

In Vim:
function g:MyCallback(param)
" process the parameter
endfunc

In Python:
vim.eval("g:MyCallback(%d)", retval)

The script doesn't actually use global functions, they are always
local to the script. The drawback is that you have to pass to Python
the name of the function to call:

In vim:
exec vxlib#plugin#MakeSID() " this is defined in VxLib, script 3061;
it defines s:SNR
function s:MyCallback(param)
" process
endfunc
python DoSomething(s:SNR . 'MyCallback', ...)

In Python:
def DoSomething(fnToCall, ...)
#...
vim.eval("%s(%d)" % (fnToCall, retval))

Marko

[Marko Mahnič]

This should probably be:
exec "python DoSomething(\"" . s:SNR . "MyCallback\", ...)"

Marko

[Tony Mechelynck]

This last one cannot be right: as a minimum, it lacks a backslash left
of "MyCallback".

Best regards,
Tony.
--
Ducharme's Axiom:
If you view your problem closely enough you will recognize
yourself as part of the problem.

[Marko Mahnič]

On 07. 06. 2011 13:39, Tony Mechelynck wrote:
> On 07/06/11 09:31, Marko Mahnič wrote:
>> On Jun 7, 9:26 am, Marko Mahnič<marko.mah...@gmail.com> wrote:
>>> On Jun 7, 8:36 am, Ivan Krasilnikov<inf...@gmail.com> wrote:
>>>
>>> function s:MyCallback(param)
>>> " process
>>> endfunc
>>> python DoSomething(s:SNR . 'MyCallback', ...)
>>
>> This should probably be:
>> exec "python DoSomething(\"" . s:SNR . "MyCallback\", ...)"
>>
>> Marko
>>
>
> This last one cannot be right: as a minimum, it lacks a backslash left
> of "MyCallback".
>

If you keep the quotes and backsalshes, but change the rest you can write (
s:SNR -> getcwd(), MyCallback -> /. ) :

:python import os
:exec "python print os.path.exists(\"" . getcwd() . "/.\")"

which works for me (Vim 7.3). If getcwd() returns "/home/user", the generated
Python statement is:

print os.path.exists("/home/user/.")

In the above case you would get the Python statement:

DoSomething("32_MyCallback", ...)

Marko

> Best regards,
> Tony.

[Tony Mechelynck]

no, you would get:
E???: invalid expression
because

>>> exec "python DoSomething(\"" . s:SNR . "MyCallback\", ...)"

string ^---------------------------------^
something Vim cannot understand ^--------...

>
>
> Marko
>
>> Best regards,
>> Tony.
--
Honk if you hate bumper stickers that say "Honk if ..."

[Tony Mechelynck]

P.S. I think you should have written

:exec 'python DoSomething("' . s:SNR . 'MyCallback", ...)'

>
>>
>>
>> Marko
>>
>>> Best regards,
>>> Tony.
--
There's nothing wrong with America that a good erection wouldn't cure.
-- David Mairowitz

[Marko Mahnič]

Let's break it down:

1. exec accepts a string
2. the string is a concatenation of 3 strings:
- "python DoSomething(\""
- s:SNR
- "MyCallback\", ...)"

The double quote is preceeded by a backslash in the first and the third string
and is treated as a part of the string. We could rewrite them as:
- 'python DoSomething("'
- 'MyCallback", ...)'

s:SNR is the SID of the script, I think it looks sth. like '42_'.

Now we concatenate:
'python DoSomething("' . '42_' . 'MyCallback", ...)'
to get
'python DoSomething("42_MyCallback", ...)'
which is a perfectly valid string for exec (but not for Python, because of the
dots which should be replaced by the actual parameters, if any).

Marko

[Marko Mahnič]

This is equivalent to the above. Note that Vim treats "" and '' strings
differently: single-quote strings are accepted as they are written while
double-quote strings undergo some fancy parsing and escaping. The following
strings are equivalent:
"\""
'"'

Marko

[Tony Mechelynck]

you forgot to backslash-escape the opening quote of "MyCallback". Third
edition. Are you blind or what? Or do you need some coffee?

>
> Marko
>

Best regards,
Tony.
--
"It was pleasant to me to get a letter from you the other day. Perhaps
I should have found it pleasanter if I had been able to decipher it. I
don't think that I mastered anything beyond the date (which I knew) and
the signature (which I guessed at). There's a singular and a perpetual
charm in a letter of yours; it never grows old, it never loses its
novelty .... Other letters are read and thrown away and forgotten, but
yours are kept forever -- unread. One of them will last a reasonable
man a lifetime."
-- Thomas Aldrich

[Tony Mechelynck]

Sorry, it's me. You're right, I'm wrong. The string ends at the second
quote after the first backslash.

>
>>
>> Marko
>>
>
> Best regards,
> Tony.
--

Please try to limit the amount of "this room doesn't have any bazingas"
until you are told that those rooms are "punched out". Once punched
out, we have a right to complain about atrocities, missing bazingas,
and such.
-- N. Meyrowitz

[Marko Mahnič]

Not blind. No need for coffee. Thanks :)

Let me describe it again:

exec "python DoSomething(\"" . s:SNR . "MyCallback\", ...)"

"python ... the opening quote for a Vim string
DoSomething(\" ... the opening quote for a Python string
" ... the closing quote for the Vim string
. s:SNR . ... concatenation
"Mycallback ... the opening quote for the 2nd Vim string
\" ... the closing quote for the Python string
, ...)" ... the closing quote for the 2nd Vim string

It's all there.

Marko

[Vlad Irnov]

On Jun 7, 12:47 am, Lenin <lenin....@gmail.com> wrote:
> Alec: It seems :py vim.command('return 1') will throw an error that says
> "return not inside a function".
>
> Marcin: Yes, I am using vim variables to transfer values from python
> functions currently, but I think this method is ugly, I'd like to know a
> better solution.

It may be ugly but it's perfectly serviceable. It can also be tricky
because the exact syntax depends on the type of value being
transfered.
For strings
:py vim.command("let g:vim_var='%s'" %python_var.replace("'", "''"))
For integers, simple dictionaries and lists:
:py vim.command("let g:vim_var=%s" %python_var)
:py vim.command("let g:vim_var=%s" %({'a':1,'b':2}))

With strings, backslashes and quotes need to be taken care of. The
easiest is to use single quotes in Vim assignment and double all
single quotes in strings. Example:

python << EOF
import vim
def py_func(): return """a'b"c\nd\t\\e"""
EOF
py print repr(py_func())
py vim.command("let g:py_var='%s'" %py_func().replace("'", "''"))
echo g:py_var

Script-local or function-local variable can be used to avoid polluting
Vim's global namespace. Python function can create Vim function-local
var when it is called from Vim function. That is, inside a Python
function:
vim.command("let l:result='%s'" %result.replace("'", "''"))

I don't think there is better solution.

[Lenin]

Thank you all, it's very helpful.

2011/6/8 Vlad Irnov <vlad....@gmail.com>

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