Adding Combobox/Dropdown List to Python Toolbox Tool Dialog?

BehrouzHosseini

I am trying to create a Python Toolbox tool which is supposed to add two fields State and StateAbb to selected Shapefile from selected combobox.

How I can add a Combobox which contains a list of US states to the Tool?

<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>
&nbsp;&nbsp;&nbsp; <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>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <SPAN class="string token">"""Define the toolbox (the name of the toolbox is the name of the
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .pyt file)."""</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; self<SPAN class="punctuation token">.</SPAN>label <SPAN class="operator token">=</SPAN> <SPAN class="string token">"states"</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; self<SPAN class="punctuation token">.</SPAN>alias <SPAN class="operator token">=</SPAN> <SPAN class="string token">"states"</SPAN>

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <SPAN class="comment token"># List of tool classes associated with this toolbox</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; self<SPAN class="punctuation token">.</SPAN>tools <SPAN class="operator token">=</SPAN> <SPAN class="punctuation token">[</SPAN>states<SPAN class="punctuation token">]</SPAN>


<SPAN class="keyword token">class</SPAN> <SPAN class="token class-name">states</SPAN><SPAN class="punctuation token">(</SPAN>object<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">:</SPAN>
&nbsp;&nbsp;&nbsp; <SPAN class="keyword token">def</SPAN> <SPAN class="token