Author benjamin.peterson
Recipients benjamin.peterson, erickt
Date 2008-07-03.12:54:09
SpamBayes Score 0.0439012
Marked as misclassified No
Message-id <1215089651.32.0.952085982722.issue3267@psf.upfronthosting.co.za>
In-reply-to
Content
This is because list comprehensions are implemented as functions in 3.0
so their scope is not leaked out to the rest of the function.

Here is the bytecode for 2.6:
>>> dis.dis(f)
  2           0 BUILD_LIST               0
              3 DUP_TOP             
              4 STORE_FAST               0 (_[1])
              7 LOAD_CONST               5 ((1, 2, 3))
             10 GET_ITER            
        >>   11 FOR_ITER                14 (to 28)
             14 STORE_FAST               1 (x)
             17 LOAD_FAST                0 (_[1])
             20 LOAD_FAST                1 (x)
             23 YIELD_VALUE         
             24 LIST_APPEND         
             25 JUMP_ABSOLUTE           11
        >>   28 DELETE_FAST              0 (_[1])
             31 STORE_FAST               1 (x)

  3          34 LOAD_CONST               4 (5)
             37 YIELD_VALUE         
             38 POP_TOP             

  4          39 LOAD_FAST                1 (x)
             42 YIELD_VALUE         
             43 POP_TOP             
             44 LOAD_CONST               0 (None)
             47 RETURN_VALUE        

and here it is for 3.0:
>>> dis.dis(f)
  2           0 LOAD_CONST               1 (<code object <listcomp> at
0x740770, file "<stdin>", line 2>) 
              3 MAKE_FUNCTION            0 
              6 LOAD_CONST               6 ((1, 2, 3)) 
              9 GET_ITER             
             10 CALL_FUNCTION            1 
             13 STORE_FAST               0 (x) 

  3          16 LOAD_CONST               5 (5) 
             19 YIELD_VALUE          
             20 POP_TOP              

  4          21 LOAD_FAST                0 (x) 
             24 YIELD_VALUE          
             25 POP_TOP              
             26 LOAD_CONST               0 (None) 
             29 RETURN_VALUE
History
Date User Action Args
2008-07-03 12:54:11benjamin.petersonsetspambayes_score: 0.0439012 -> 0.0439012
recipients: + benjamin.peterson, erickt
2008-07-03 12:54:11benjamin.petersonsetspambayes_score: 0.0439012 -> 0.0439012
messageid: <1215089651.32.0.952085982722.issue3267@psf.upfronthosting.co.za>
2008-07-03 12:54:10benjamin.petersonlinkissue3267 messages
2008-07-03 12:54:09benjamin.petersoncreate