This is the error I receive from the PythonCaller:

Python Exception <ValueError>: 'L' is not in list

Traceback (most recent call last):

File "<string>", line 22, in input

ValueError: 'L' is not in list

Error encountered while calling method `input'

PythonCaller_3 (PythonFactory): PythonFactory failed to process feature

Here is the python in the PythonCaller: it's reading two attributes from the ListBuilder. This runs on the same data without error in FME 2017

# Template Class Interface:

# When using this class, make sure its name is set as the value of

# the 'Class or Function to Process Features' transformer parameter

class FeatureProcessor(object):

def __init__(self):

pass

def input(self,feature):

self.listC = feature.getAttribute('_list{}.c')

self.listL = feature.getAttribute('_list{}.l')

self.list = zip(self.listC,self.listL)

#

if self.list != None:

self.check = =]

for i,e in enumerate(self.list):

if e 1] == 'M':

self.check.append(e(0])

if not self.check:

self.add = =]

for i,e in enumerate(self.list):

self.add.append(e(1])

val = self.add.index('L') + 1

for i,e in enumerate(self.list):

x = i + 1

if x == val:

feature.setAttribute('_list{%d}.l' %i,'M')

self.pyoutput(feature)

def close(self):

pass