Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>True, <em>most programming languages</em> make parameter order part of the function call contract, but this doesn't <em>need</em> to be so. Why would it? My understanding of the question is, then, if Python is any different to other programming languages in this respect. In addition to other good answers for Python 2, please consider the following:</p> <pre><code>__named_only_start = object() def info(param1,param2,param3,_p=__named_only_start,spacing=10,collapse=1): if _p is not __named_only_start: raise TypeError("info() takes at most 3 positional arguments") return str(param1+param2+param3) +"-"+ str(spacing) +"-"+ str(collapse) </code></pre> <p>The only way a caller would be able to provide arguments <code>spacing</code> and <code>collapse</code> positionally (without an exception) would be:</p> <pre><code>info(arg1, arg2, arg3, module.__named_only_start, 11, 2) </code></pre> <p>The convention of not using private elements belonging to other modules already is very basic in Python. As with Python itself, this convention for parameters would only be semi-enforced.</p> <p>Otherwise, calls would need to be of the form:</p> <pre><code>info(arg1, arg2, arg3, spacing=11, collapse=2) </code></pre> <p>A call</p> <pre><code>info(arg1, arg2, arg3, 11, 2) </code></pre> <p>would assign value 11 to parameter <code>_p</code> and an exception risen by the function's first instruction.</p> <p>Characteristics:</p> <ul> <li>Parameters before <code>_p=__named_only_start</code> are admitted positionally (or by name).</li> <li>Parameters after <code>_p=__named_only_start</code> must be provided by name only (unless knowledge about the special sentinel object <code>__named_only_start</code> is obtained and used).</li> </ul> <p>Pros:</p> <ul> <li>Parameters are explicit in number and meaning (the later if good names are also chosen, of course).</li> <li>If the sentinel is specified as first parameter, then all arguments need to be specified by name.</li> <li>When calling the function, it's possible to switch to positional mode by using the sentinel object <code>__named_only_start</code> in the corresponding position.</li> <li>A better performance than other alternatives can be anticipated.</li> </ul> <p>Cons:</p> <ul> <li><s>Checking occurs during run-time, not compile-time.</s></li> <li>Use of an extra parameter (though not argument) and an additional check. Small performance degradation respect to regular functions.</li> <li>Functionality is a hack without direct support by the language (see note below).</li> <li>When calling the function, it's possible to switch to positional mode by using the sentinel object <code>__named_only_start</code> in the right position. Yes, this can also be seen as a pro.</li> </ul> <p>Please do keep in mind that this answer is only valid for Python 2. Python 3 implements the similar, but very elegant, language-supported mechanism described in other answers.</p> <p>I've found that when I open my mind and think about it, no question or other's decision seems stupid, dumb, or just silly. Quite on the contrary: I typically learn a lot.</p>
    singulars
    1. This table or related slice is empty.
    1. POForced naming of parameters in Python
      singulars
      1. PTQuestion
    1. PTAnswer
    1. USCœur
    1. USMario Rossi
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    1. CO_"Checking occurs during run-time, not compile-time."_ - I think that's true of all function argument checking. Until you actually execute the line of the function invocation, you don't always know which function is being executed. Also, **+1** - this is clever.
      singulars
      1. PO
      1. USEric
    2. CO@Eric: It's just that I'd have preferred static checking. But you are right: that wouldn't have been Python at all. Though not a decisive point, Python 3's "*" construct is also dynamically checked. Thanks for your comment.
      singulars
      1. PO
      1. USMario Rossi
    3. COAlso, if you name the module variable `_named_only_start`, it becomes impossible to reference it from an external module, which takes out a pro and a con. (single leading underscores at module scope are private, IIRC)
      singulars
      1. PO
      1. USEric
 

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