[Python-ideas] Augment dis.dis to autocompile strings

[Nick Coghlan]

Steven D'Aprano wrote:
> On Fri, 17 Jul 2009 04:35:40 am Terry Reedy wrote:
> 
>> Proposal: if the input is a string, do the above (do what I mean)
>> instead of raising
>> TypeError: don't know how to disassemble str objects
>>
>> Any negatives before I submit a feature request?
> 
> +1 on the idea, but how do you determine which of the following are 
> required?
> 
> compile('x+1', '', 'eval')
> compile('x = x+1', '', 'single')
> compile('while x < 42: x += 1', '', 'exec')
> 
> 
> Or do you just assume 'exec'?

We could define it as trying the three in order (first 'eval', then
'single', then 'exec') moving on to the next option if it raises syntax
error:

from dis import dis
def dis_str(source):
  modes = ('eval', 'single', 'exec')
  for mode in modes:
    try:
      c = compile(source, '', mode)
      break
    except SyntaxError:
      if mode is modes[-1]:
        raise
  return dis(c)

>>> dis_str("x+1")
  1           0 LOAD_NAME                0 (x)
              3 LOAD_CONST               0 (1)
              6 BINARY_ADD
              7 RETURN_VALUE
>>> dis_str("x = x+1")
  1           0 LOAD_NAME                0 (x)
              3 LOAD_CONST               0 (1)
              6 BINARY_ADD
              7 STORE_NAME               0 (x)
             10 LOAD_CONST               1 (None)
             13 RETURN_VALUE
>>> dis_str("while x < 42: x += 1")
  1           0 SETUP_LOOP              26 (to 29)
        >>    3 LOAD_NAME                0 (x)
              6 LOAD_CONST               0 (42)
              9 COMPARE_OP               0 (<)
             12 POP_JUMP_IF_FALSE       28
             15 LOAD_NAME                0 (x)
             18 LOAD_CONST               1 (1)
             21 INPLACE_ADD
             22 STORE_NAME               0 (x)
             25 JUMP_ABSOLUTE            3
        >>   28 POP_BLOCK
        >>   29 LOAD_CONST               2 (None)
             32 RETURN_VALUE
>>> dis_str("bad syntax still goes boom")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 5, in dis_str
  File "", line 1
    bad syntax still goes boom
             ^
SyntaxError: invalid syntax

Cheers,
Nick.

-- 
Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia
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