# Constructed Tag Path is Invalid **URL:** \ **Category:** Ignition\ **Tags:** ignition81, perspective, scripting\ **Created:** [December 30, 2024, 11:43pm UTC](https://forum.inductiveautomation.com/t/constructed-tag-path-is-invalid/100327 "2024-12-30T23:43:12Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![Eric\_Li](https://avatars.discourse-cdn.com/v4/letter/e/9d8465/32.png) [@Eric\_Li](https://forum.inductiveautomation.com/u/Eric_Li)\ **Post date:** [December 30, 2024, 11:43pm UTC](https://forum.inductiveautomation.com/t/constructed-tag-path-is-invalid/100327/1 "2024-12-30T23:43:12Z")
Hello there, I am trying to generate a valid tag path for the tagPaths parameter of system.tag.readBlocking function. The tag path I want to use is [Default]AI\_LT1. The path does work If I generate the string in the following way ```python path = "[Default]AI_LT1" result = system.tag.readBlocking(path) ``` However, if I tended to generate the same path by combining one variable that contains a pre-defined value with a string component, the path is invalid then. There is the example code: ```python tag_raw = self.props.selection.active.data[0]['displayPath'] tag_index = tag_raw.find('-') tag_trimmed = tag_raw[:tag_index] path = tag_trimmed + "AI_LT1" result = system.tag.readBlocking(path) ``` * * * In this case, tag\_trimmed is equal to [Default] and will display [Default]AI\_LT1 if print (path). However, it fails to read the proper tag content as what I type in the path = ''[Default]AI\_LT1" directly. I tried some initial troubleshooting by using str (path) or .encode('utf-8') to return a string or unicode datatype but no luck. Any idea why it happens? Thanks for the help! ---
**Author:** ![David\_Stone](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/david_stone/32/79749_2.png) [@David\_Stone](https://forum.inductiveautomation.com/u/David_Stone)\ **Post date:** [December 30, 2024, 11:51pm UTC](https://forum.inductiveautomation.com/t/constructed-tag-path-is-invalid/100327/2 "2024-12-30T23:51:35Z")
Can you show us the text contained in `self.props.selection.active.data[0]['displayPath']` ? It is a little hard to follow what you are trying to achieve here. ---
**Author:** ![ryan.white](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/ryan.white/32/73193_2.png) [@ryan.white](https://forum.inductiveautomation.com/u/ryan.white)\ **Post date:** [December 30, 2024, 11:55pm UTC](https://forum.inductiveautomation.com/t/constructed-tag-path-is-invalid/100327/3 "2024-12-30T23:55:26Z")
Add `print type(tag_trimmed)` to see if it is actually the type that you are expecting. Also try `print type(path)` to confirm its a string. `system.tag.readBlocking` expects a list of tag paths. It allows you to pass a single string to avoid breaking projects from older versions that got upgraded. It might not like something about how you are constructing the string, so try using `result = system.tag.readBlocking([path])` Also consider using java's string formatting to generate the path, ie: `path = "%sAI_LT1" % tag_trimmed` ---
**Author:** ![Eric\_Li](https://avatars.discourse-cdn.com/v4/letter/e/9d8465/32.png) [@Eric\_Li](https://forum.inductiveautomation.com/u/Eric_Li)\ **Post date:** [December 31, 2024, 12:23am UTC](https://forum.inductiveautomation.com/t/constructed-tag-path-is-invalid/100327/4 "2024-12-31T00:23:30Z")
Thanks for the rely!Tthe text contained in `self.props.selection.active.data[0]['displayPath'] is a PyUnicode with text [Default] - Alarm/Hi/Alarm:/alm:Alarm. After trimming, tag\_trimmed is then equal to [Default]. ---
**Author:** ![David\_Stone](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/david_stone/32/79749_2.png) [@David\_Stone](https://forum.inductiveautomation.com/u/David_Stone)\ **Post date:** [December 31, 2024, 12:26am UTC](https://forum.inductiveautomation.com/t/constructed-tag-path-is-invalid/100327/5 "2024-12-31T00:26:17Z")
Change this: `tag_index = tag_raw.find('-') ` to this: `tag_index = tag_raw.find('-') -1` You are including a space between the `[Default]` and the tag path. ---
**Author:** ![Eric\_Li](https://avatars.discourse-cdn.com/v4/letter/e/9d8465/32.png) [@Eric\_Li](https://forum.inductiveautomation.com/u/Eric_Li)\ **Post date:** [December 31, 2024, 12:27am UTC](https://forum.inductiveautomation.com/t/constructed-tag-path-is-invalid/100327/6 "2024-12-31T00:27:18Z")
Hello Ryan, thanks for the reply! the data type of path was PyUnicode. I tried use str(path) which supposes to return a PyString data type but still doesn't work. I will try the rest methods you mentioned later the. ---
**Author:** ![ryan.white](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/ryan.white/32/73193_2.png) [@ryan.white](https://forum.inductiveautomation.com/u/ryan.white)\ **Post date:** [December 31, 2024, 12:29am UTC](https://forum.inductiveautomation.com/t/constructed-tag-path-is-invalid/100327/7 "2024-12-31T00:29:30Z")
Safer method might be to call `.strip()` on the result of the original trim, I can foresee someone not including that space between `[Default]` and the `-`. ---
**Author:** ![Eric\_Li](https://avatars.discourse-cdn.com/v4/letter/e/9d8465/32.png) [@Eric\_Li](https://forum.inductiveautomation.com/u/Eric_Li)\ **Post date:** [December 31, 2024, 5:54pm UTC](https://forum.inductiveautomation.com/t/constructed-tag-path-is-invalid/100327/8 "2024-12-31T17:54:43Z")
By applying either of your solutions @David_Stone @ryan.white and removing the space in between, the path is working properly now. Really appreciate the help!