Databases
StackOverflow2013
Postsdbo
POPython safe dict navigation, The Right Way
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POPython safe dict navigation, The Right Way
    primarykey
    data
    text
    <h1>TLDR summary</h1> <p>I wrote a function <code>navigateDict</code> that does a safe navigation on a <code>dict</code>, similar to <code>dict.get()</code> but nested. It replaces code like</p> <pre><code>if 1 in data and 'i' in data[1] and 'a' in data[1]['i']: print data[1]['i']['a'] else: print "Not found" </code></pre> <p>with the roughly equivalent</p> <pre><code>found = navigateDict(data, 1, 'i', 'a') if found is not None: print found else: print "Not found" </code></pre> <ul> <li>Is anything similar to this already part of the standard library?</li> <li>Is there a more idiomatic way to do the same thing? <ul> <li>Any response that requires typing any path component key more than once is probably a non-answer.</li> </ul></li> </ul> <h1>Additional details</h1> <p>The implementation is as follows:</p> <pre><code># Allow fallback value other than None def navigateDictEx(d, keys, fallback=None): for key in keys: if key in d: d = d[key] else: return fallback return d def navigateDict(d, *keys): return navigateDictEx(d, keys) </code></pre> <p>See the summary for example usage.</p> <p>Pythonic or not, this function reduces repetition in a place where redundancy is a bad idea. For example, changing one path component in the example requires up to three distinct values to be modified as one in the original example, but only one in the modified example. Given my regular tendency to err, this is a big win.</p> <p>Ultimately I'm asking this: Is there something in the standard library that does this, or am I going to need to find a place for it in my project's library?</p> <h1>If hits are expected to dominate misses</h1> <p>brionius correctly points out that catching <code>KeyError</code> will work:</p> <pre><code>try: print data[1]['i']['a'] except KeyError: print "Not found" </code></pre> <p>This might be the way I go; it's pretty terse and cuts the repetition. However, it does reflect an assumption that there will be more hits than misses. If there's a better way of assuming the opposite I'd like to know that, also.</p>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. USpsmay
    1. USpsmay
    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. PO
      singulars
      1. PTAnswer
    2. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. POPython safe dict navigation, The Right Way
      1. This table or related slice is empty.
      1. VTUpMod
    1. This table or related slice is empty.
 

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