# How to parse null parameters in scripts **URL:** \ **Category:** Ignition\ **Tags:** perspective\ **Created:** [January 7, 2025, 6:27pm UTC](https://forum.inductiveautomation.com/t/how-to-parse-null-parameters-in-scripts/100552 "2025-01-07T18:27:50Z")\ **Posts on this page:** 13\ **Page:** 1
**Author:** ![Noah\_Gilgo](https://avatars.discourse-cdn.com/v4/letter/n/c89c15/32.png) [@Noah\_Gilgo](https://forum.inductiveautomation.com/u/Noah_Gilgo)\ **Post date:** [January 7, 2025, 6:27pm UTC](https://forum.inductiveautomation.com/t/how-to-parse-null-parameters-in-scripts/100552/1 "2025-01-07T18:27:50Z")
I'm trying to write a script transform that will take the JSON below and delete any leaf nodes with `{label: null}`. ```python [ { "icon": { "path": "XXX", "style": {}, "color": "" }, "expanded": true, "label": "XXX", "data": { "EqType": XXX, "EqEnabled": true, "EqName": "XXX", "EqPath": "XXX", "EqID": 1 }, "items": [ { "icon": { "path": "XXX/XXX", "style": {}, "color": "" }, "expanded": true, "label": "XXX", "data": { "EqType": "XXX", "EqEnabled": true, "EqName": "XXX", "EqPath": "XXX/XXX", "EqID": 1 }, "items": [ { "icon": { "path": "XXX/XXX", "style": {}, "color": "var(--error)" }, "expanded": false, "label": "QA Test Area", "data": { "EqType": "XXX", "EqEnabled": false, "EqName": "QA Test Area", "EqPath": "XXX/XXX/XXX", "EqID": 11 }, "items": [ { "icon": { "path": "material/block", "style": {}, "color": "var(--error)" }, "expanded": false, "label": null, "data": { "EqType": "XXX", "EqEnabled": null, "EqName": null, "EqPath": null, "EqID": null }, "items": [] } ] } ] } ] } ] ``` However, I have not been able to figure out a way to write a Python conditional that checks if `label: null`. This is what I attempted to do in the if statement below: ```python def transform(self, value, quality, timestamp): for enterprise in value: for site in enterprise["items"]: for area in site["items"]: for line in area["items"]: if line["label"] == None: del line ``` If someone could tell me how to check if a perspective property is null in Python, that would be very helpful. ---
**Author:** ![danieltalbot](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/danieltalbot/32/11201_2.png) [@danieltalbot](https://forum.inductiveautomation.com/u/danieltalbot)\ **Post date:** [January 7, 2025, 6:31pm UTC](https://forum.inductiveautomation.com/t/how-to-parse-null-parameters-in-scripts/100552/2 "2025-01-07T18:31:46Z")
try if line["label"] is None: or if not line["label"]: ---
**Author:** ![kvane](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/kvane/32/22228_2.png) [@kvane](https://forum.inductiveautomation.com/u/kvane)\ **Post date:** [January 7, 2025, 6:34pm UTC](https://forum.inductiveautomation.com/t/how-to-parse-null-parameters-in-scripts/100552/3 "2025-01-07T18:34:50Z")
You should review the error(s) you are seeing closely, I am guessing you are seeing things like: name 'null' is not defined, etc. You are not dealing with a None, you are dealing with a variable written as "null", if you want it to be treated as None then set that variable at the start of the script: null = None This is also true for variables like "true" because Python's true bool is: True ---
**Author:** ![Noah\_Gilgo](https://avatars.discourse-cdn.com/v4/letter/n/c89c15/32.png) [@Noah\_Gilgo](https://forum.inductiveautomation.com/u/Noah_Gilgo)\ **Post date:** [January 7, 2025, 6:42pm UTC](https://forum.inductiveautomation.com/t/how-to-parse-null-parameters-in-scripts/100552/4 "2025-01-07T18:42:31Z")
I'm not getting any errors when I run the script. My problem is that I would like for the script to delete any nodes with `label: null` from the json tree, but the script is not doing so, instead returning the initial json tree with zero modifications whatsoever. ---
**Author:** ![kvane](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/kvane/32/22228_2.png) [@kvane](https://forum.inductiveautomation.com/u/kvane)\ **Post date:** [January 7, 2025, 6:45pm UTC](https://forum.inductiveautomation.com/t/how-to-parse-null-parameters-in-scripts/100552/5 "2025-01-07T18:45:41Z")
Did you remove the return at the end of the transform? > **[Script Transform | Ignition User Manual](https://www.docs.inductiveautomation.com/docs/8.1/ignition-modules/perspective/working-with-perspective-components/bindings-in-perspective/transforms/script-transform)** > > Script Transforms are special functions that are applied only on an existing binding. They take the result of a binding (or transform) as an input and produce a single output. This will allow you to manipulate a binding result using whatever python... > It is assumed the custom script will end with a Return comment that is a single output value, dataset, document, or other type of data. ---
**Author:** ![Noah\_Gilgo](https://avatars.discourse-cdn.com/v4/letter/n/c89c15/32.png) [@Noah\_Gilgo](https://forum.inductiveautomation.com/u/Noah_Gilgo)\ **Post date:** [January 7, 2025, 6:54pm UTC](https://forum.inductiveautomation.com/t/how-to-parse-null-parameters-in-scripts/100552/6 "2025-01-07T18:54:54Z")
I've ensured that there is a return statement at the end of the transform. I also cloned `value` into the return variable `tree` to ensure that the code is not returning the original `value` variable. ```python def transform(self, value, quality, timestamp): tree = value[:] for enterprise in tree: for site in enterprise["items"]: for area in site["items"]: for line in area["items"]: if line["label"] == None: del line return tree ``` Unfortunately. I'm still getting the same behavior. `tree` still contains the item ```python { "icon": { "path": "material/block", "style": {}, "color": "var(--error)" }, "expanded": false, "label": null, "data": { "EqType": "line", "EqEnabled": null, "EqName": null, "EqPath": null, "EqID": null }, "items": [] } ``` with `label: null` that I am trying to remove from the json tree. ---
**Author:** ![paul-griffith](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/paul-griffith/32/37249_2.png) [@paul-griffith](https://forum.inductiveautomation.com/u/paul-griffith)\ **Post date:** [January 7, 2025, 7:02pm UTC](https://forum.inductiveautomation.com/t/how-to-parse-null-parameters-in-scripts/100552/7 "2025-01-07T19:02:07Z")
What @danieltalbot said. JSON defines "a key with no value" with the keyword `null` (not in quotes). Python defines the same concept as a singleton object automatically imported as `None`. The idiomatic way to check whether something is null/not present _in Python_ is with `if x is None:` or `if x is not None:`. ---
**Author:** ![Noah\_Gilgo](https://avatars.discourse-cdn.com/v4/letter/n/c89c15/32.png) [@Noah\_Gilgo](https://forum.inductiveautomation.com/u/Noah_Gilgo)\ **Post date:** [January 7, 2025, 7:09pm UTC](https://forum.inductiveautomation.com/t/how-to-parse-null-parameters-in-scripts/100552/8 "2025-01-07T19:09:34Z")
Like this? ```python def transform(self, value, quality, timestamp): tree = value[:] for enterprise in tree: for site in enterprise["items"]: for area in site["items"]: for line in area["items"]: label = line["label"] if label is None: del line return tree ``` I attempted this, but the code is acting the same as before. It is not deleting the `line` node with `label: null` from `tree`. ---
**Author:** ![danieltalbot](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/danieltalbot/32/11201_2.png) [@danieltalbot](https://forum.inductiveautomation.com/u/danieltalbot)\ **Post date:** [January 7, 2025, 7:19pm UTC](https://forum.inductiveautomation.com/t/how-to-parse-null-parameters-in-scripts/100552/9 "2025-01-07T19:19:10Z")
I'm guessing that area["items"] is an array of line objects. Try this: ```python def transform(self, value, quality, timestamp): tree = value[:] for enterprise in tree: for site in enterprise["items"]: for area in site["items"]: for i, line in enumerate(area["items"]): label = line["label"] if label is None: del area[i] return tree ``` ---
**Author:** ![Noah\_Gilgo](https://avatars.discourse-cdn.com/v4/letter/n/c89c15/32.png) [@Noah\_Gilgo](https://forum.inductiveautomation.com/u/Noah_Gilgo)\ **Post date:** [January 7, 2025, 7:32pm UTC](https://forum.inductiveautomation.com/t/how-to-parse-null-parameters-in-scripts/100552/10 "2025-01-07T19:32:28Z")
I attempted your code, and it seems to be attempting to perform the deletion, thankfully. However, the script errors out because the del statement throws the error `TypeError: 'com.inductiveautomation.perspective.gateway.script.DotReferenceJythonMap' object doesn't support item deletion` ---
**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:** [January 7, 2025, 8:37pm UTC](https://forum.inductiveautomation.com/t/how-to-parse-null-parameters-in-scripts/100552/11 "2025-01-07T20:37:29Z")
You need to make a copy of the tree, probably recursively, where you simply do not copy the items you would otherwise delete. ---
**Author:** ![Noah\_Gilgo](https://avatars.discourse-cdn.com/v4/letter/n/c89c15/32.png) [@Noah\_Gilgo](https://forum.inductiveautomation.com/u/Noah_Gilgo)\ **Post date:** [January 7, 2025, 8:56pm UTC](https://forum.inductiveautomation.com/t/how-to-parse-null-parameters-in-scripts/100552/12 "2025-01-07T20:56:59Z")
So far, the only working solution I've managed is by converting `value` from a `JsonifiableArrayList` to a `List[Dict]`, then using a `line_index` variable and the `pop()` method to remove the line from the area. ```python def transform(self, value, quality, timestamp): import json tree = value[:][0].toString() tree = [json.loads(tree)] for enterprise in tree: for site in enterprise["items"]: for area in site["items"]: line_index = 0 for line in area["items"]: label = line["label"] if label is None: area["items"].pop(line_index) line_index += 1 return tree ``` For some reason, the `del` keyword does not remove the line from the `items` list, but `pop()` does. ---
**Author:** ![pascal.fragnoud](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/pascal.fragnoud/32/24728_2.png) [@pascal.fragnoud](https://forum.inductiveautomation.com/u/pascal.fragnoud)\ **Post date:** [January 9, 2025, 10:21am UTC](https://forum.inductiveautomation.com/t/how-to-parse-null-parameters-in-scripts/100552/13 "2025-01-09T10:21:42Z")
```python def transform(self, value, quality, timestamp): for enterprise in value: for site in enterprise["items"]: for area in site["items"]: area['items'] = filter(lambda l: l['label'] is not None, area['items']) # area['items'] = [l for l in area['items'] if l['label'] is not None] return value ``` Didn't try it but I believe it should do what you want. In comment, a comprehension version if that looks clearer to you.