Python UiPath - How to use Classes with UiPath.Python.Activities

Question

Here is an image showing Python scope activity (version 3.6 and target x64):

Python Scope

The main problem is the relation between both invoke python methods, the first one is used to start the class object, and the second one to access a method of that class. Here is an image of the first invoke python properties:

Invoke Python init method

And the getNumberPlusOne activity call:

Invoke Python getNumberPlusOne method

The python code being executed:

class ExampleClass: def __init__(self,t,n): self.text = t self.number = n def getNumberPlusOne(self): return (self.number+1)

And finally, the error when executing the second Invoke Python Method:

An ExceptionDetail, likely created by IncludeExceptionDetailInFaults=true, whose value is: System.InvalidOperationException: Error invoking Python method ----> System.Runtime.Serialization.InvalidDataContractException: Type 'UiPath.Python.PythonObject' cannot be serialized. Consider marking it with the DataContractAttribute attribute, and marking all of its members you want serialized with the DataMemberAttribute attribute. If the type is a collection, consider marking it with the CollectionDataContractAttribute. See the Microsoft .NET Framework documentation for other supported types.

Any idea about where is the mistake and how to interact with the output object created in the init method?

Answer 1

here is the Load Python Script activity: 

In my case the local variable "pyScript" is a pointer to the python object, i.e. an instance of ExampleClass.

Now, there is the Invoke Python Method activity but methods on the class are inaccessible to UiPath -you can't just type pyScript.MethodName(). 

use another method outside your class in order to access or manipulate your object:

class ExampleClass:
    def __init__(self,t,n):
        self.text = t
        self.number = n

    def getNumberPlusOne(self):
        return (self.number+1)


foo = ExampleClass("bar", 42)

def get_number_plus_one():
    return foo.getNumberPlusOne()