Re: #line in python (dirty tricks)
Duncan Booth wrote Ross Boylan ross at biostat.ucsf.edu wrote: As an extension or alternate, could there be a decorator like @source_line(lineno, filename) for classes and methods that could do the conversion on the fly? I don't know if there's a way to go from the function (or class) object the decorator receives to the AST. No [easy] way to go from bytecodes back to AST, but I see no reason why you can't create a new code object with your filename and line numbers and then create a new function using your modified code object. Could you elaborate? I don't understand what you are suggesting. If you don't have a 1:1 correspondence of lines then you'll need to pick out all the existing line numbers from the code object co_lnotab and modify them: see dis.py findlinestarts() for how to do this. Classes would be harder: the decorator doesn't run until after the class body has executed, so you can't change the line numbers that way until it's too late. The only thing I can think would be to put all of the generated code inside a function and fix up that function with a decorator that scans the bytecode to find all contained classes and fix them up. Or you could generate a .pyc file and then fix up line numbers in the whole file: see http://nedbatchelder.com/blog/200804/the_structure_of_pyc_files.html for some code that shows you what's in a .pyc My latest concept is to produce code that rewrites itself. Suppose the naive file would be --- mycode.py (naive) class SomeClass: class comment def some_function(self, bar): pass - end --- Protect that code by putting an if 0: in front of it and indenting each line one space. Than prepend a bit of code to do the rewriting, and add indicators of the original line numbers. --- mycode.py (after wrapping) - from detangle import detangle detangle(mycode.py, mycode.nw) if 0: # original code goes here class SomeClass: class comment #and when line numbering changes #line 35 def some_function(self, bar): pass - end --- I would write detangle so that it scans through the file in which it appears (named in the first argument), rewriting so that it appears to come from the original file (mycode.nw) given in the second argument. The scanning would look for the if 0: in the file. At that point it would accumulate code by reading lines and stripping the leading space. If it found a #line directive it would remember it and then remove it from the string it was accumulating. Finally, detangle would would pass the string of code to ast.compile, catching any syntax errors and rewriting the file and line number (I might rewrite columns too with an extension) and then rethrowing them. If compilation succeeded detangle could rewrite the AST and then exec it. Ross -- http://mail.python.org/mailman/listinfo/python-list
Re: #line in python (dirty tricks)
Ross Boylan r...@biostat.ucsf.edu wrote: No [easy] way to go from bytecodes back to AST, but I see no reason why you can't create a new code object with your filename and line numbers and then create a new function using your modified code object. Could you elaborate? I don't understand what you are suggesting. This (written for Python 3.x, needs some attribute names changing for Python 2.x: import functools def source_line(lineno, filename = None): def decorator(f): c = f.__code__ code = type(c)( c.co_argcount, c.co_kwonlyargcount, c.co_nlocals, c.co_stacksize, c.co_flags, c.co_code, c.co_consts, c.co_names, c.co_varnames, c.co_filename if filename is None else filename, c.co_name, lineno, c.co_lnotab, c.co_freevars, c.co_cellvars) f.__code__ = code return f return decorator @source_line(43, 'foo.bar') def foo(): This is foo for i in range(10): bar() @source_line(665, 'evil.txt') def bar(): raise RuntimeError(oops) if __name__=='__main__': import traceback try: foo() except RuntimeError as ex: traceback.print_exc() When you run it the output looks something like this (if you create a file evil.txt with 667 lines): Traceback (most recent call last): File C:\temp\foo.py, line 30, in module foo() File foo.bar, line 47, in foo File evil.txt, line 667, in bar Evil line 667 RuntimeError: oops -- Duncan Booth http://kupuguy.blogspot.com -- http://mail.python.org/mailman/listinfo/python-list
