Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>It's perfectly legit. </p> <p>The "<a href="http://docs.python.org/library/stdtypes.html#string-formatting-operations" rel="nofollow noreferrer">single argument</a>" form of the string formatter is really a special case - for multiple items a tuple is normally used and that would lead to a more obvious example of why it's ok </p> <pre><code>result = "%s limit 1" % (sql % (table,),) </code></pre> <p><em>This ^ was originally written to encourage the questioner that supporting multiple-formats was a legitimate language feature but, as Nas Banov comments, it does read like I'm trying to explain how it works (not helped by screwing up the code). It doesn't build the string right to left like this suggests it might, but HAS to build it (be associative) left to right. The operator must take a string on the left and return one, but can take a non-string (a tuple) on the right. Since you can't use % on a pair of tuples it can't possibly work in reverse</em></p> <pre><code>&gt;&gt;&gt; "%s %f %s" % ( "%d", 0.1, "%d %d" ) % (1,2,3) '1 0.100000 2 3' </code></pre> <p>It may, however, lead to complicated/messy code, so personally I would use it very sparingly.</p> <p>You could work your example like this:</p> <pre><code>def get_sql(table, limit=True): sql = "select report_date from" strlimit = "" if limit: strlimit = "limit 1" return "%s %s"%(sql, strlimit) </code></pre>
    singulars
    1. This table or related slice is empty.
    1. POChained string formatting in Python
      singulars
      1. PTQuestion
    1. PTAnswer
    1. USpycruft
    1. USpycruft
    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
    3. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    1. CO`--`: Wrong explanation, this has nothing to do with multiple arguments and the associativeness is wrong. Try `"%ss limit 1" % '%' % 'BOO'` to see what i mean, this expression works, whenever if we put parenthesis as you suggest, `"%ss limit 1" % ('%' % ('BOO'))` breaks/error. Also, your proposed fix is no better than the original
      singulars
      1. PO
      1. USNas Banov
    2. COI think you've misunderstood. I wasn't suggesting it had anything to do with the singularity or multiplicity of the arguments, just that if you changed from using singles to tuples it would become more clear that it's a legit thing to do. Your counter example is wrong - ('%' % ('BOO')) isn't valid. `"%s limit 1" % '%s' % 'BOO'` versus `"%s limit 1" % ('%s' % ('BOO'))`. Both work. Note that question doesn't contain the `%ss` format your example needs. That isn't a 'proposed fix' - there's nothing wrong with the original code, it's just a suggested change.
      singulars
      1. PO
      1. USpycruft
    3. COSeems like you don't get it. (A) Putting the parenthesis the way you did changes the **order of operations**. When you have expression of the kind `A % B % C`, it is executed as `(A % B) % C`, not as `A % (B % C)`, as your first set of parens forces it to. (B) Also, your understanding that putting () around expression makes tuple out of it is wrong - it doesn't. To force tuple you either have to explicitly use constructor `tuple()`, or use a "silly comma", like so `"%s limit 1" % (sql % (table,),)` - that will create tuples but your example will still be wrong because of (A)
      singulars
      1. PO
      1. USNas Banov
 

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