# Create list from a bigger list **URL:** \ **Category:** Ignition\ **Created:** [November 15, 2019, 2:18am UTC](https://forum.inductiveautomation.com/t/create-list-from-a-bigger-list/29980 "2019-11-15T02:18:53Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![ematschke](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/ematschke/32/7544_2.png) [@ematschke](https://forum.inductiveautomation.com/u/ematschke)\ **Post date:** [November 15, 2019, 2:18am UTC](https://forum.inductiveautomation.com/t/create-list-from-a-bigger-list/29980/1 "2019-11-15T02:18:54Z")
Is there a simple way to make a new partial list from an existing bigger list, but in a different order? I have ```auto myList = ["blue", "red", "green", "orange"] ``` if If try ```auto myNewList = myList[0:2] print myNewLIst ``` blue, red how do i get blue and green trying not to do ```auto myNewList = [myList[0]] myNewList.append([myList[2]) ``` this is a simplified example of much bigger lists. ---
**Author:** ![witman](https://avatars.discourse-cdn.com/v4/letter/w/d2c977/32.png) [@witman](https://forum.inductiveautomation.com/u/witman)\ **Post date:** [November 15, 2019, 3:27am UTC](https://forum.inductiveautomation.com/t/create-list-from-a-bigger-list/29980/2 "2019-11-15T03:27:30Z")
This would return blue and green from your example: ```auto myList = ["blue", "red", "green", "orange"] # Extract every 2nd item from first list. myNewList = myList[0::2] print myNewList ``` But I'm guessing you're not looking for every second item. > [@ematschke](#): > > this is a simplified example of much bigger lists What kind of criteria/pattern would you use to select items from the old list for the new list? ---
**Author:** ![pturmel](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/pturmel/32/3295_2.png) [@pturmel](https://forum.inductiveautomation.com/u/pturmel)\ **Post date:** [November 15, 2019, 12:45pm UTC](https://forum.inductiveautomation.com/t/create-list-from-a-bigger-list/29980/3 "2019-11-15T12:45:03Z")
If you have another list containing the indices you want, you can use a list comprehension: ```auto myList = ["blue", "red", "green", "orange"] mySubscripts = [0, 2] myNewList = [myList[x] for x in mySubscripts] ``` You should be aware that you were mis-using both slicing and the .append() method in your OP, yielding a list within a list in both cases. Spend some time in the python docs for [sequence types](https://docs.python.org/2.7/library/stdtypes.html#sequence-types-str-unicode-list-tuple-bytearray-buffer-xrange) for the details. ---
**Author:** ![ematschke](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/ematschke/32/7544_2.png) [@ematschke](https://forum.inductiveautomation.com/u/ematschke)\ **Post date:** [November 15, 2019, 3:06pm UTC](https://forum.inductiveautomation.com/t/create-list-from-a-bigger-list/29980/4 "2019-11-15T15:06:54Z")
Correct. The source list contains 14 items, but I want to pull out five of them in the order 2,9,3,0,1 so my SQL query will return items in the order I want to display in a table component. my other option was ```auto vals = myList[2] vals.append(myList[9]) vals.append(myList[3]) vals.append(myList[0]) or optionally vals.append(myList[0:2]) vals.append(myList[1]) ``` I think that is correct now I was hoping there was a simple single line way to do it As @pturmel pointed out, my OP was incorrect. I wrote that out as I was trying to leave the office. I guess I should also figure out how to post code snippets properly as you all have done. ---
**Author:** ![pturmel](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/pturmel/32/3295_2.png) [@pturmel](https://forum.inductiveautomation.com/u/pturmel)\ **Post date:** [November 15, 2019, 3:27pm UTC](https://forum.inductiveautomation.com/t/create-list-from-a-bigger-list/29980/5 "2019-11-15T15:27:59Z")
> [@ematschke](#): > > I think that is correct now Nope. Missing brackets and errors with .append() still present. Starting here: ```auto vals = myList[2] vals.append(myList[9]) ``` `vals` is not a list. So `.append()` won't work the way you think. (With the above, it is a string, so `.append()` is expected to add a character to it.) And the latter `.append()` below, if `vals` was actually a list instead of a string: ```auto vals.append(myList[0]) or optionally vals.append(myList[0:2]) ``` is adding a slice of `myList` (which is a two-element list) as a single element of `vals`, nesting it. It would yield something like `[a, [b, c]]`. Please, read up on how brackets work in python in the linked documentation. ---
**Author:** ![pturmel](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/pturmel/32/3295_2.png) [@pturmel](https://forum.inductiveautomation.com/u/pturmel)\ **Post date:** [November 15, 2019, 3:31pm UTC](https://forum.inductiveautomation.com/t/create-list-from-a-bigger-list/29980/6 "2019-11-15T15:31:27Z")
> [@ematschke](#): > > I guess I should also figure out how to post code snippets properly as you all have done. Place a line with just three backquote characters above your code, and again below your code. Like so: ``` `# Some code` ``` You can edit your prior posts to include these and they'll magically become readable. ---
**Author:** ![witman](https://avatars.discourse-cdn.com/v4/letter/w/d2c977/32.png) [@witman](https://forum.inductiveautomation.com/u/witman)\ **Post date:** [November 15, 2019, 3:47pm UTC](https://forum.inductiveautomation.com/t/create-list-from-a-bigger-list/29980/7 "2019-11-15T15:47:23Z")
With that short list, you can one-line it like this (combining 2nd & 3rd lines of @pturmel's example): ```python vals = [myList[x] for x in [2, 9, 3, 0, 1]] ``` In your latter example, your first line would need to look like this to make it a list (rather than a string): ```auto vals = [myList[2]] ``` To get the expected result from this line: > [@ematschke](#): > > vals.append(myList[0:2]) You'd need to replace `append` with `extend`. ---
**Author:** ![ematschke](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/ematschke/32/7544_2.png) [@ematschke](https://forum.inductiveautomation.com/u/ematschke)\ **Post date:** [November 15, 2019, 5:13pm UTC](https://forum.inductiveautomation.com/t/create-list-from-a-bigger-list/29980/8 "2019-11-15T17:13:05Z")
I think I get it This works ```auto selCols = project.globalVars.PART_STANDARDS_COLS[0:] # get all columns print selCols whereCols = [project.globalVars.PART_STANDARDS_COLS[0]] # Where column 0 and 2, . partNo and ViewID whereCols.append(project.globalVars.PART_STANDARDS_COLS[2]) # LAME print whereCols table = "PARTSTANDARDS" retValA,pyDataSet1 = project.db.dml.selectData(selCols,whereCols,whereVals,table,database) # don't need optional order or sort ``` and so does this, but for different reasons ```auto selCols = project.globalVars.PART_COORDS_COLS[0:] # get all columns, create new list print selCols # print result whereCols = project.globalVars.PART_COORDS_COLS[0:2] # Where column 0 and 1, . partNo and ViewID, create new list print whereCols # print result table = "PARTCOORDS" # table retValB,pyDataSet2 = project.db.dml.selectData(selCols,whereCols,whereVals,table,database) # don't need optional order or sort ``` it depends if the “:” is present in the list reference whether the result is a list or a string, among other things. The source lists are pre-defined in script modules