pop() method returns error with feature class list in ArcGIS python toolbox

Question

I am trying to do something very simple, but I'm pulling my hair out with this one.

In an ArcGIS python toolbox, for one of my tools I ask the user for a list of feature layers, using the following code in the .pyt file:

    def getParameterInfo(self):
    """Define parameter definitions"""
    param0 = arcpy.Parameter(
        displayName="Input Line Networks",
        name="InputFCList",
        datatype="GPFeatureLayer", 
        parameterType="Required",
        direction="Input",
        multiValue=True)
    param0.filter.list = ["Polyline"]

The key parameter here is multiValue=True. Then, in my function (where InputFCList is sent), I use this code to pop off the first item in the list of feature classes:

def main(fcList, fcBndPoly, boolSeg, fcOutCombine):
    fcToLine = fcList.pop
    # rest of the code...

This code runs fine during testing, when I hard-coded the list of feature classes. However, when running the tool in ArcMap, I get the following error:

AttributeError: 'unicode' object has not attribute 'pop'

According to the ESRI documentation, setting the multiValue parameter to True should allow for the creation of a list of input feature classes, but there's obviously something else going on if it thinks the list is actually a unicode object. Any ideas?

Answer 1

You haven't shown how you received the parameter value, but I would guess you're likely using parameters[n].valueAsText. Use parameters[n].values instead to receive the value back as a list.