Databases
StackOverflow2013
Postsdbo
POBest method for changing a list while iterating over it
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POBest method for changing a list while iterating over it
    primarykey
    data
    text
    <p>I have several instances in a python script (v2.6) where I need to modify a list in-place. I need to pop values from the list in response to interactive input from the user and would like to know the cleanest method of doing this. Currently I have the very dirty solutions of a) setting items in the list that I want to remove to False and removing them with a filter or list comprehension or b) generating an entirely new list while going through the loop, which seems to be needlessly adding variables to the namespace and taking up memory.</p> <p>An example of this problem is as follows:</p> <pre><code>for i, folder in enumerate(to_run_folders): if get_size(folder) &lt; byte_threshold: ans = raw_input(('The folder {0}/ is less than {1}MB.' + \ ' Would you like to exclude it from' + \ ' compression? ').format(folder, megabyte_threshold)) if 'y' in ans.strip().lower(): to_run_folders.pop(i) </code></pre> <p>I would like to look at each folder in the list. If the current folder is less than a certain size, I want to ask the user if they want to exclude it. If they do, pop the folder from the list.</p> <p>The problem with this routine is that if I iterate over the list, I get unexpected behavior and early termination. If I iterate over a copy by slicing, pop doesn't pull the right value because the indices are shifted and the problem compounds as more items are popped. I have a need for dynamic list adjustment of this kind in other areas of my script as well. Is there any clean method for this kind of functionality?</p>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. This table or related slice is empty.
    1. USPatrick
    plurals
    1. PL
      singulars
      1. LTLinked
    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
    3. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. POBest method for changing a list while iterating over it
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. POBest method for changing a list while iterating over it
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. POBest method for changing a list while iterating over it
      1. This table or related slice is empty.
      1. VTUpMod
    1. COStick with your *dirty* solution. It is clearly the fastest one, and the less problematic.
      singulars
      1. POBest method for changing a list while iterating over it
      1. USpepr
 

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