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Global value can't be assigned inside the expression in python toolbox

AarthiBalamurugan1

I am trying to call the global value 'total_rows' inside the expression. But I am getting an error.

and my code is

def execute(self, parameters, messages):
"""The source code of the tool."""
   inputdataset = parameters[0].valueAsText #getting the parameters

   count_rows = arcpy.GetCount_management(inputdataset)
   total_rows = int(count_rows.getOutput(0))

expression = '''

   def getCitation(p_dataset_id):
      global total_rows
      if(total_rows == 5):
            ds=PanDataSet(p_dataset_id)
   return ds.citation

'''

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Luke_Pinner

It's a string expression and is evaluated outside the scope of your current code so has no knowledge about any of your variables.

You need to insert the actual value into the string:

<SPAN class="keyword token">class</SPAN> <SPAN class="token class-name">YourTool</SPAN><SPAN class="punctuation token">(</SPAN>object<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">:</SPAN>
    <SPAN class="keyword token">def</SPAN> <SPAN class="token function">__init__</SPAN><SPAN class="punctuation token">(</SPAN>self<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">:</SPAN>
        etc<SPAN class="punctuation token">.</SPAN><SPAN class="punctuation token">.</SPAN><SPAN class="punctuation token">.</SPAN>

    <SPAN class="keyword token">def</SPAN> <SPAN class="token function">getParameterInfo</SPAN><SPAN class="punctuation token">(</SPAN>self<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">:</SPAN>
        etc<SPAN class="punctuation token">.</SPAN><SPAN class="punctuation token">.</SPAN><SPAN class="punctuation token">.</SPAN>

    <SPAN class="keyword token">def</SPAN> <SPAN class="token function">execute</SPAN><SPAN class="punctuation token">(</SPAN>self<SPAN class="punctuation token">,</SPAN> parameters<SPAN class="punctuation token">,</SPAN> messages<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">:</SPAN>
        <SPAN class="string token">"""The source code of the tool."""</SPAN>
    
        inputdataset <SPAN class="operator token">=</SPAN> parameters<SPAN class="punctuation token">[</SPAN><SPAN class="number token">0</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">.</SPAN>valueAsText  <SPAN class="comment token"># getting the parameters</SPAN>
    
        count_rows <SPAN class="operator token">=</SPAN> arcpy<SPAN class="punctuation token">.</SPAN>GetCount_management<SPAN class="punctuation token">(</SPAN>inputdataset<SPAN class="punctuation token">)</SPAN>
        total_rows <SPAN class="operator token">=</SPAN> int<SPAN class="punctuation token">(</SPAN>count_rows<SPAN class="punctuation token">.</SPAN>getOutput<SPAN class="punctuation token">(</SPAN><SPAN class="number token">0</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">)</SPAN>
    
        expression <SPAN class="operator token">=</SPAN> <SPAN class="string token">'''
def getCitation(p_dataset_id):
  total_rows = {}
  if(total_rows == 5):
      ds=PanDataSet(p_dataset_id)
      return ds.citation
'''</SPAN><SPAN class="punctuation token">.</SPAN>format<SPAN class="punctuation token">(</SPAN>total_rows<SPAN class="punctuation token">)</SPAN>
‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍<SPAN class="line-numbers-rows"><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN></SPAN>

Note - you can't indent the expression, or it won't be valid python syntax when the tool evaluates it - IndentationError: unexpected indent. If you want your code to look cleaner and have the expression indented, you can use inspect.cleandoc(expression)

inspect — Python 2.7 documentation

inspect — Python 3.8 documentation

inspect.cleandoc(doc)
Clean up indentation from docstrings that are indented to line up with blocks of code.
All leading whitespace is removed from the first line. Any leading whitespace that can be uniformly removed from the second line onwards is removed. Empty lines at the beginning and end are subsequently removed. Also, all tabs are expanded to spaces.

<SPAN class="keyword token">import</SPAN> inspect

<SPAN class="keyword token">class</SPAN> <SPAN class="token class-name">YourTool</SPAN><SPAN class="punctuation token">(</SPAN>object<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">:</SPAN>
    <SPAN class="keyword token">def</SPAN> <SPAN class="token function">__init__</SPAN><SPAN class="punctuation token">(</SPAN>self<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">:</SPAN>
        etc<SPAN class="punctuation token">.</SPAN><SPAN class="punctuation token">.</SPAN><SPAN class="punctuation token">.</SPAN>

    <SPAN class="keyword token">def</SPAN> <SPAN class="token function">getParameterInfo</SPAN><SPAN class="punctuation token">(</SPAN>self<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">:</SPAN>
        etc<SPAN class="punctuation token">.</SPAN><SPAN class="punctuation token">.</SPAN><SPAN class="punctuation token">.</SPAN>

    <SPAN class="keyword token">def</SPAN> <SPAN class="token function">execute</SPAN><SPAN class="punctuation token">(</SPAN>self<SPAN class="punctuation token">,</SPAN> parameters<SPAN class="punctuation token">,</SPAN> messages<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">:</SPAN>
        <SPAN class="string token">"""The source code of the tool."""</SPAN>
    
        inputdataset <SPAN class="operator token">=</SPAN> parameters<SPAN class="punctuation token">[</SPAN><SPAN class="number token">0</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">.</SPAN>valueAsText  <SPAN class="comment token"># getting the parameters</SPAN>
    
        count_rows <SPAN class="operator token">=</SPAN> arcpy<SPAN class="punctuation token">.</SPAN>GetCount_management<SPAN class="punctuation token">(</SPAN>inputdataset<SPAN class="punctuation token">)</SPAN>
        total_rows <SPAN class="operator token">=</SPAN> int<SPAN class="punctuation token">(</SPAN>count_rows<SPAN class="punctuation token">.</SPAN>getOutput<SPAN class="punctuation token">(</SPAN><SPAN class="number token">0</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">)</SPAN>
    
        expression <SPAN class="operator token">=</SPAN> inspect<SPAN class="punctuation token">.</SPAN>cleandoc<SPAN class="punctuation token">(</SPAN><SPAN class="string token">'''
            def getCitation(p_dataset_id):
                total_rows = {}
                if(total_rows == 5):
                    ds=PanDataSet(p_dataset_id)
                    return ds.citation
        '''</SPAN><SPAN class="punctuation token">.</SPAN>format<SPAN class="punctuation token">(</SPAN>total_rows<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">)</SPAN>‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍<SPAN class="line-numbers-rows"><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN></SPAN>

RandyBurton

Did you try something like indicating that total_rows was a global in the "execute" function (line 3) below:

<SPAN class="keyword token">def</SPAN> <SPAN class="token function">execute</SPAN><SPAN class="punctuation token">(</SPAN>self<SPAN class="punctuation token">,</SPAN> parameters<SPAN class="punctuation token">,</SPAN> messages<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">:</SPAN>
<SPAN class="string token">"""The source code of the tool."""</SPAN>
   <SPAN class="keyword token">global</SPAN> total_rows <SPAN class="comment token"># indicate that total_rows is a global</SPAN>
   inputdataset <SPAN class="operator token">=</SPAN> parameters<SPAN class="punctuation token">[</SPAN><SPAN class="number token">0</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">.</SPAN>valueAsText <SPAN class="comment token">#getting the parameters</SPAN>

   count_rows <SPAN class="operator token">=</SPAN> arcpy<SPAN class="punctuation token">.</SPAN>GetCount_management<SPAN class="punctuation token">(</SPAN>inputdataset<SPAN class="punctuation token">)</SPAN>
   total_rows <SPAN class="operator token">=</SPAN> int<SPAN class="punctuation token">(</SPAN>count_rows<SPAN class="punctuation token">.</SPAN>getOutput<SPAN class="punctuation token">(</SPAN><SPAN class="number token">0</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">)</SPAN>

expression <SPAN class="operator token">=</SPAN> <SPAN class="string token">'''

   def getCitation(p_dataset_id):
      global total_rows
      if(total_rows == 5):
            ds=PanDataSet(p_dataset_id)
   return ds.citation

'''</SPAN><SPAN class="line-numbers-rows"><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN></SPAN>

I'm also puzzled by the indentation in the code snippet you posted. Is the "expression" section (lines 9 -17) part of the "execute" function? It may not be indented properly.

AarthiBalamurugan1

No It didn't work as well. I am getting the same error. If it is outside the expression it works.

Right now I am just testing the code whether the global values can be assigned inside the expression.

I am sending the dataset id value to the server to collect the data. Within 30 seconds the server can handle 60 data if it is more than that it stops working.

So I want to get the total number of rows and if it's more than 60 rows I want to delay the processing.

DanPatterson_Retired

expression <SPAN class="operator token">=</SPAN> <SPAN class="string token">''</SPAN>'
   <SPAN class="keyword token">global</SPAN> total_rows
   total_rows<SPAN class="operator token">=</SPAN><SPAN class="number token">5</SPAN>
   <SPAN class="keyword token">def</SPAN> <SPAN class="token function">getCitation</SPAN><SPAN class="punctuation token">(</SPAN>p_dataset_id<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">:</SPAN>
      <SPAN class="keyword token">if</SPAN><SPAN class="punctuation token">(</SPAN>total_rows <SPAN class="operator token">==</SPAN> <SPAN class="number token">5</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">:</SPAN>
            ds<SPAN class="operator token">=</SPAN>PanDataSet<SPAN class="punctuation token">(</SPAN>p_dataset_id<SPAN class="punctuation token">)</SPAN>
   <SPAN class="keyword token">return</SPAN> ds<SPAN class="punctuation token">.</SPAN>citation‍‍‍‍‍‍‍‍‍‍‍‍<SPAN class="line-numbers-rows"><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN></SPAN>

so this didn't work either?

But I am not sure what it is the script is doing since there is nowhere in the script that collects information to compare to total rows

AarthiBalamurugan1

Inside the expression the global value is not working. I want to get the number of row values inside the expression.

DanPatterson_Retired

you need to assign an initial value to the global somewhere, like outside the def in your enclosing expression

RandyBurton

Using globals in a Python toolbox or script tool is a bit tricky. The toolbox/script creates a number of instances during function calls. It is best to declare a global in getParameterInfo as this function appears to be called only once. An example of a toolbox script that uses "junk" as a global variable is:

<SPAN class="keyword token">import</SPAN> arcpy

<SPAN class="keyword token">class</SPAN> <SPAN class="token class-name">Toolbox</SPAN><SPAN class="punctuation token">(</SPAN>object<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">:</SPAN>
    <SPAN class="keyword token">def</SPAN> <SPAN class="token function">__init__</SPAN><SPAN class="punctuation token">(</SPAN>self<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">:</SPAN>
        self<SPAN class="punctuation token">.</SPAN>label <SPAN class="operator token">=</SPAN> <SPAN class="string token">"Toolbox"</SPAN>
        self<SPAN class="punctuation token">.</SPAN>alias <SPAN class="operator token">=</SPAN> <SPAN class="string token">""</SPAN>
        self<SPAN class="punctuation token">.</SPAN>tools <SPAN class="operator token">=</SPAN> <SPAN class="punctuation token">[</SPAN>Tool<SPAN class="punctuation token">]</SPAN>


<SPAN class="keyword token">class</SPAN> <SPAN class="token class-name">Tool</SPAN><SPAN class="punctuation token">(</SPAN>object<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">:</SPAN>
    <SPAN class="keyword token">def</SPAN> <SPAN class="token function">__init__</SPAN><SPAN class="punctuation token">(</SPAN>self<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">:</SPAN>
        self<SPAN class="punctuation token">.</SPAN>label <SPAN class="operator token">=</SPAN> <SPAN class="string token">"Tool"</SPAN>
        self<SPAN class="punctuation token">.</SPAN>description <SPAN class="operator token">=</SPAN> <SPAN class="string token">""</SPAN>
        self<SPAN class="punctuation token">.</SPAN>canRunInBackground <SPAN class="operator token">=</SPAN> <SPAN class="token boolean">False</SPAN>

    <SPAN class="keyword token">def</SPAN> <SPAN class="token function">getParameterInfo</SPAN><SPAN class="punctuation token">(</SPAN>self<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">:</SPAN>
        <SPAN class="keyword token">global</SPAN> junk
        junk <SPAN class="operator token">=</SPAN> None
        param0 <SPAN class="operator token">=</SPAN> arcpy<SPAN class="punctuation token">.</SPAN>Parameter<SPAN class="punctuation token">(</SPAN>
            displayName<SPAN class="operator token">=</SPAN><SPAN class="string token">"Something"</SPAN><SPAN class="punctuation token">,</SPAN>
            name<SPAN class="operator token">=</SPAN><SPAN class="string token">"something"</SPAN><SPAN class="punctuation token">,</SPAN>
            datatype<SPAN class="operator token">=</SPAN><SPAN class="string token">"GPString"</SPAN><SPAN class="punctuation token">,</SPAN>
            parameterType<SPAN class="operator token">=</SPAN><SPAN class="string token">"Required"</SPAN><SPAN class="punctuation token">,</SPAN>
            direction<SPAN class="operator token">=</SPAN><SPAN class="string token">"Input"</SPAN>
        <SPAN class="punctuation token">)</SPAN>
        params <SPAN class="operator token">=</SPAN> <SPAN class="punctuation token">[</SPAN>param0<SPAN class="punctuation token">]</SPAN>
        <SPAN class="keyword token">return</SPAN> params

    <SPAN class="keyword token">def</SPAN> <SPAN class="token function">isLicensed</SPAN><SPAN class="punctuation token">(</SPAN>self<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">:</SPAN>
        <SPAN class="keyword token">return</SPAN> <SPAN class="token boolean">True</SPAN>

    <SPAN class="keyword token">def</SPAN> <SPAN class="token function">updateParameters</SPAN><SPAN class="punctuation token">(</SPAN>self<SPAN class="punctuation token">,</SPAN> parameters<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">:</SPAN>
        <SPAN class="keyword token">global</SPAN> junk
        junk <SPAN class="operator token">=</SPAN> <SPAN class="string token">"XYZ"</SPAN>
        <SPAN class="keyword token">return</SPAN>

    <SPAN class="keyword token">def</SPAN> <SPAN class="token function">updateMessages</SPAN><SPAN class="punctuation token">(</SPAN>self<SPAN class="punctuation token">,</SPAN> parameters<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">:</SPAN>
        <SPAN class="keyword token">return</SPAN>

    <SPAN class="keyword token">def</SPAN> <SPAN class="token function">execute</SPAN><SPAN class="punctuation token">(</SPAN>self<SPAN class="punctuation token">,</SPAN> parameters<SPAN class="punctuation token">,</SPAN> messages<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">:</SPAN>
        <SPAN class="keyword token">global</SPAN> junk
        arcpy<SPAN class="punctuation token">.</SPAN>AddMessage<SPAN class="punctuation token">(</SPAN><SPAN class="string token">"The value junk is: "</SPAN> <SPAN class="operator token">+</SPAN> junk<SPAN class="punctuation token">)</SPAN>
        <SPAN class="keyword token">return</SPAN><SPAN class="line-numbers-rows"><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN></SPAN>

For more discussion see the following:

Using Global Variables in Python Toolbox?

Python toolbox tool objects do not remember instance variables between function calls?

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