# MalformedJsonException: Invalid escape sequence

**URL:** <https://forum.inductiveautomation.com/t/malformedjsonexception-invalid-escape-sequence/89737>\
**Category:** Ignition\
**Tags:** scripting, vision\
**Created:** [April 30, 2024, 8:40pm UTC](https://forum.inductiveautomation.com/t/malformedjsonexception-invalid-escape-sequence/89737 "2024-04-30T20:40:02Z")\
**Posts on this page:** 6\
**Page:** 1

<div class="post-metadata">

**Author:** ![Devin\_Golberg](https://avatars.discourse-cdn.com/v4/letter/d/6f9a4e/32.png) [@Devin\_Golberg](https://forum.inductiveautomation.com/u/Devin_Golberg)\
**Post date:** [April 30, 2024, 8:40pm UTC](https://forum.inductiveautomation.com/t/malformedjsonexception-invalid-escape-sequence/89737/1 "2024-04-30T20:40:02Z")

</div>

I'm running into an issue while trying to add text to templates, via passed parameters, that are then added to a template canvas, at runtime. The code works great until it encounters certain special characters, such as the degree symbol, at which point it starts throwing `WARN Vision.TemplateCanvas - Unable to parse parameters as JSON on row X `(where X is the row #)`. MalformedJsonException: Invalid escape sequence at line 1 column 35`.

The code I've been working with to add a line to a dataset that tells the template canvas how to create the cell is below:

```python
	rowData = {"rid":5,"description":"45° angle"}
	def buildDescCell(this):
		tid = "rid" + str(this.rowData["rid"]) + "-" + str(1) # A unique name for the template being added to the canvas
		template = "TATemplate" # The name of the template being used; this one's a TextArea, but same happens with basic Labels
		constraints = "grow,cell 1 1 1 1,w 50px" #This line is simplified for this example...
		inputStr = this.rowData["description"].replace('°', '') #Works until the .replace() is removed/commented out
		params = {"tempID": tid ,"text": inputStr} #Parameters to be passed to the template being added to the TemplateCanvas
		cList = [tid,template,constraints,0,0,None,None,params] #The final construction of the TemplateCanvas data for a single cell to be added
		return cList #Returned data is added to tableData = [] via tableData.append(data)

```

Now the above code works as it is, but as soon as you remove/comment out the `.replace('°', '')` call on 'inputStr' is when the MalformedJsonException errors start getting thrown by the TemplateCanvas object.

To put the data into the TemplateCanvas, I convert it to a usable dataset using:

```python
dsHeader = ["name","template","layout","x","y","width","height","parameters"]
def getTableDataSet(this):
	data = system.dataset.toDataSet(this.dsHeader, this.tableData)
	print data.getValueAt(66,7) # The line in question; Returns: {'tempID': 'rid5-1', 'text': '45\xc2\xb0 Angle'}
	return data # Inside of a button `TemplateCanvas.templates = <this returned dataSet>` applies the dataset to the template canvas in order to display the cells.

```

What am I doing wrong that's causing this to throw the exception? I'm guessing I need to encode the symbol differently, but I'm not sure what is acceptable to get it to stop throwing json exceptions but still display the ° symbol.

I've tried:

```python
import json
...
json.dumps(inputStr) 
...

```

which gets rid of the error, but then I get the string: `"45\u00b0 Angle"` showing up in my TextArea/Label, "" included. I've also tried `unicode(inputStr,"utf-8")`, but that breaks even more text in other cells. I've run out of ideas to try...

I've seen this thread: [Degree Symbol not supported in system.util.jsonDecode?](https://forum.inductiveautomation.com/t/degree-symbol-not-supported-in-system-util-jsondecode/34527) But still can't seem to get anything working. I feel like I'm missing something right in front of my face, but am too frustrated to see it...

---

<div class="post-metadata">

**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:** [April 30, 2024, 9:01pm UTC](https://forum.inductiveautomation.com/t/malformedjsonexception-invalid-escape-sequence/89737/2 "2024-04-30T21:01:48Z")

</div>

You are using jython's json module. Jython's stdlib is known to be mostly broken when unicode is involved. Don't use it.

Use the Ignition-supplied `system` functions instead.

Also, wherever you might provide unicode symbols in jython string constants, make sure you mark them as unicode with the `u"some ° String"` syntax.

---

<div class="post-metadata">

**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:** [April 30, 2024, 9:05pm UTC](https://forum.inductiveautomation.com/t/malformedjsonexception-invalid-escape-sequence/89737/3 "2024-04-30T21:05:28Z")

</div>

> [@pturmel](#):
>
> Also, wherever you might provide unicode symbols in jython string constants, make sure you mark them as unicode with the `u"some ° String"` syntax.

I think that's the biggest problem here.  
Pasting `45° angle` directly into the template canvas customizer works fine for me:

 ![image](https://us1.discourse-cdn.com/inductiveautomation/original/3X/8/a/8a479cb3e36d13d25e1addee3bac6b2104dd51c6.png)

---

<div class="post-metadata">

**Author:** ![Devin\_Golberg](https://avatars.discourse-cdn.com/v4/letter/d/6f9a4e/32.png) [@Devin\_Golberg](https://forum.inductiveautomation.com/u/Devin_Golberg)\
**Post date:** [April 30, 2024, 10:18pm UTC](https://forum.inductiveautomation.com/t/malformedjsonexception-invalid-escape-sequence/89737/4 "2024-04-30T22:18:25Z")

</div>

I kind of figured it wasn't the ° symbol, as I have another piece of code that's far more convoluted (this code is my attempt at cleaning that up, but turned into a complete rewrite...) that doesn't throw the error, but I also don't specify in either one to use the system.util vs Jython's stdlib, so I'm not sure why that code works and this doesn't.

What in the code I showed points it to using the Jython stdlib? If you're referring solely to the `import json` part, that's only something I've tried on the side and is not in use when I get the error.

Update: I looked a little closer at my old code and noticed I was passing the parameters as a stringified dictionary in my old code, whereas this code uses an actual dictionary for the params. Converting it to a stringified dict fixes the issue.

ie:

```python
params = {"tempID": tid ,"text": inputStr}

```

is now:

```python
params = '{"tempID":'+tid+',"text":"'+unicode(inputStr)+'"}'

```

and this works fine while displaying the ° symbol. Without `unicode()` works, but I get the extra character `45° Angle` before the degree symbol like I struggled with prior. So my mistake was using an actual dictionary, not a string representing a dictionary, like I had in my old code. The odd part was that it worked until special characters were introduced...

---

<div class="post-metadata">

**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:** [April 30, 2024, 10:30pm UTC](https://forum.inductiveautomation.com/t/malformedjsonexception-invalid-escape-sequence/89737/5 "2024-04-30T22:30:02Z")

</div>

Make a regular ol' Python data structure, using unicode subsequences as appropriate, and convert to json with `system.util.jsonEncode` at the "last moment" before inserting into the template canvas dataset:

```python
params = {
	"text": u"90° angle"
}

headers = ["name","template","parameters","x","y","width","height","layout","z"]
data = [[
	"abc",
	"label",
	system.util.jsonEncode(params),
	0,
	0,
	200,
	200,
	"n/a",
	0
]]

ds = system.dataset.toDataSet(headers, data)
event.source.parent.getComponent('Template Canvas').templates = ds

```

![image](https://us1.discourse-cdn.com/inductiveautomation/original/3X/c/1/c142ca1377fca9785d5c0d1ed98ed14c2ce64f4e.png)

---

<div class="post-metadata">

**Author:** ![Devin\_Golberg](https://avatars.discourse-cdn.com/v4/letter/d/6f9a4e/32.png) [@Devin\_Golberg](https://forum.inductiveautomation.com/u/Devin_Golberg)\
**Post date:** [April 30, 2024, 10:40pm UTC](https://forum.inductiveautomation.com/t/malformedjsonexception-invalid-escape-sequence/89737/6 "2024-04-30T22:40:29Z")

</div>

I was just testing that, myself, lol... Heck of a lot quicker to type out, and easier to read, than the manual string conversion.

Could've swore I'd tried that at one point but it didn't work... probably was a typo somewhere.