Python - check syntax and run script

Tip 733 Printable Monobook Previous Next

created 2004 · complexity basic · author Rene Aguirre · version 5.7

---

I just discovered Vim, I really liked 'split' capability, I'm so used to edit Python source code on SciTe editor, I really missed the default CTRL-1 to check the sintax and F5 to run the script...

So, this is my suggestion, add these lines to your vimrc file:

autocmd BufRead *.py set makeprg=python\ -c\ \"import\ py_compile,sys;\ sys.stderr=sys.stdout;\ py_compile.compile(r'%')\"
autocmd BufRead *.py set efm=%C\ %.%#,%A\ \ File\ \"%f\"\\,\ line\ %l%.%#,%Z%[%^\ ]%\\@=%m
autocmd BufRead *.py nmap <F5> :!python %<CR>

Make your that python is in your path, now when you open any python file just type ":make" to get the syntax errors, use ":cnext", to move to next error, check the help on make (":help make") for more info on how to navigate errors.

As you are checking now, <F5> is mapped to execute the current script. Also I suggest you to use add the following lines to vimrc:

autocmd BufRead *.py set tabstop=4
autocmd BufRead *.py set nowrap
autocmd BufRead *.py set go+=b

That will make to use a 4 spaces for you tabstop (only visually), it avoids wrapping your code and will add a bottom scrollbar. Now I like vim a litle bit more.

Comments

How about having the line:

nmap <buffer> <F5> :w<Esc>mwG:r!python %<CR>`.

in the file $VIM/vimfiles/ftplugin/python.vim?

(I have the preceding line with 'python' replaced by 'perl' in the file $VIM/vimfiles/ftplugin/perl.vim )

(The adjective <buffer> in the map of <F5> restricts the map to the buffer. The map of <F5> as given in the tip is "permanent" in the sense that after opening a *.py file, the map remains for other non-*.py files.

Also, putting the map in a ftplugin-file means that it is available even when the python file-type is detected by means other than the .py extension -- means such as the command ':set ft=python' or the shebang.)

---

The counterpart of python's sys.stderr=sys.stdout in perl is the following line placed toward the beginning of the perl file:

BEGIN {(*STDERR = *STDOUT) || die;}

The preceding is needed so that the 'r' in the map of <F5> can capture stuff in stderr.

---

Here's a script that automatically checks the syntax while saving and refuses to save files with syntax errors. Mildly hacky but it seems to work just fine.

" Define the current compiler
if exists("compiler")
  finish
endif
let compiler = "python"

" Set python as the make program and
setlocal makeprg=python
setlocal errorformat=%C\ %.%#,%A\ \ File\ \"%f\"\\,\ line\ %l%.%#,%Z%[%^\ ]%\\@=%m

" When writing Python file check the syntax
au! BufWriteCmd *.py call CheckPythonSyntax()

function CheckPythonSyntax()
  " Write the current buffer to a temporary file, check the syntax and
  " if no syntax errors are found, write the file
  let curfile = bufname("%")
  let tmpfile = tempname()
  silent execute "write! ".tmpfile
  let output = system("python -c \"__import__('py_compile').compile(r'".tmpfile."')\" 2>&1")
  if output != ''
    " Make sure the output specifies the correct filename
    let output = substitute(output, fnameescape(tmpfile), fnameescape(curfile), "g")
    echo output
  else
    write
  endif
  " Delete the temporary file when done
  call delete(tmpfile)
endfunction