Databases
StackOverflow2013
Postsdbo
POHow should I understand the output of dis.dis?
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POHow should I understand the output of dis.dis?
    primarykey
    data
    text
    <p>I would like to understand how to use <a href="http://docs.python.org/library/dis.html" rel="noreferrer">dis (the dissembler of Python bytecode)</a>. Specifically, how should one interpret the output of <a href="http://docs.python.org/library/dis.html#dis.dis" rel="noreferrer"><code>dis.dis</code></a> (or <a href="http://docs.python.org/library/dis.html#dis.disassemble" rel="noreferrer"><code>dis.disassemble</code></a>)?</p> <p>.</p> <p><em>Here is a very specific example (in Python 2.7.3):</em></p> <pre class="lang-py prettyprint-override"><code>dis.dis("heapq.nsmallest(d,3)") 0 BUILD_SET 24933 3 JUMP_IF_TRUE_OR_POP 11889 6 JUMP_FORWARD 28019 (to 28028) 9 STORE_GLOBAL 27756 (27756) 12 LOAD_NAME 29811 (29811) 15 STORE_SLICE+0 16 LOAD_CONST 13100 (13100) 19 STORE_SLICE+1 </code></pre> <p>I see that <a href="http://docs.python.org/library/dis.html#opcode-JUMP_IF_TRUE_OR_POP" rel="noreferrer"><code>JUMP_IF_TRUE_OR_POP</code></a> etc. are bytecode instructions <em>(although interestingly, <code>BUILD_SET</code> does not appear in this list, though I expect it works as <a href="http://docs.python.org/library/dis.html#opcode-BUILD_TUPLE" rel="noreferrer"><code>BUILD_TUPLE</code></a>)</em>. I think the numbers on the right-hand-side are memory allocations, and the numbers on the left are <a href="http://en.wikipedia.org/wiki/GOTO" rel="noreferrer">goto</a> numbers... I notice they <em>almost</em> increment by 3 each time (but not quite).</p> <p>If I wrap <code>dis.dis("heapq.nsmallest(d,3)")</code> inside a function:</p> <pre class="lang-py prettyprint-override"><code>def f_heapq_nsmallest(d,n): return heapq.nsmallest(d,n) dis.dis("f_heapq(d,3)") 0 BUILD_TUPLE 26719 3 LOAD_NAME 28769 (28769) 6 JUMP_ABSOLUTE 25640 9 &lt;44&gt; # what is &lt;44&gt; ? 10 DELETE_SLICE+1 11 STORE_SLICE+1 </code></pre>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. USAndy Hayden
    1. USAndy Hayden
    plurals
    1. PL
      singulars
      1. LTLinked
    1. PL
      singulars
      1. LTLinked
    2. PL
      singulars
      1. LTLinked
    3. PL
      singulars
      1. LTLinked
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. POHow should I understand the output of dis.dis?
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. POHow should I understand the output of dis.dis?
      1. UStripleee
      1. VTFavorite
    3. VO
      singulars
      1. POHow should I understand the output of dis.dis?
      1. This table or related slice is empty.
      1. VTUpMod
    1. COsee also: http://stackoverflow.com/questions/3299648/python-compilation-interpretation-process
      singulars
      1. POHow should I understand the output of dis.dis?
      1. USAndy Hayden
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload