Transfer python dictionnary between 2 Transformers

You can either define your dictionary as a global variable:

global my_dict
my_dict = {1: 'a', 2: 'b', 3: 'c'}

Then in a different Python transformer you can access it like this:

global my_dict
my_value = my_dict[1]

Alternatively you can pass the dictionary as JSON strings from one transformer to another using the feature attributes.

To convert a dictionary "my_dict" to JSON and store it in the attribute "my_json":

feature.setAttribute('my_json', json.dumps(my_dict))

Then later on you can read the attribute "my_json" and convert it back to a dictionary:

my_dict = json.loads(feature.getAttribute('my_json))

You can either define your dictionary as a global variable:

global my_dict
my_dict = {1: 'a', 2: 'b', 3: 'c'}

Then in a different Python transformer you can access it like this:

global my_dict
my_value = my_dict[1]

Alternatively you can pass the dictionary as JSON strings from one transformer to another using the feature attributes.

To convert a dictionary "my_dict" to JSON and store it in the attribute "my_json":

feature.setAttribute('my_json', json.dumps(my_dict))

Then later on you can read the attribute "my_json" and convert it back to a dictionary:

my_dict = json.loads(feature.getAttribute('my_json))

I also added my_json in the Attributes to Expose. Is that right?

By the way, I'm new on this forum. Do I have to answer in the comment or in a new answer?

Thanks. But, I have a error in my log saying that the dictionnary isn't a string.

I checked printing the type of it. In the Creator, it is a string. But in the Caller, it became a NonType.

global myDict

Is that because I'm doing it in a method in a class?

Thanks. But, I have a error in my log saying that the dictionnary isn't a string.

I checked printing the type of it. In the Creator, it is a string. But in the Caller, it became a NonType.

global myDict

Is that because I'm doing it in a method in a class?

Try this instead:

import json
import fmeobjects

class FeatureCreator(object):

    def __init__(self):
        pass

    def close(self):
        feature = fmeobjects.FMEFeature()
        myDict = {'Commune' : 'Tokyo'}
        feature.setAttribute('my_json', json.dumps(myDict))
        self.pyoutput(feature)

Notice how self.pyoutput(feature) always comes last.

Also notice that you have to import the json module.

If you attach a Logger after this PythonCreator you should get:

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Feature Type: `Logger_LOGGED'
Attribute(string): `fme_feature_type' has value `PythonCreator'
Attribute(string): `my_json' has value `{"Commune": "Tokyo"}'
Geometry Type: Unknown (0)
===========================================================================

Hope this helps.

Perfect. Thanks a lot.

Someone at my place told me that I can create my dictionnary in a startup python script. Is that a correct use? I find the json method cleaner.

What do you think?

Apples and oranges.

If the dictionary stays the same during the entire translation, I'd just make it a global variable or something like that. You can create a global variable wherever you want, basically, including in a startup script.

If the dictionary is feature specific, I'd go the JSON route.

Hi @slerendu, found two issues.

• A global variable should be declared in the method definition that refers to the variable. In this case, you have to declare the 'myDict' global variable in the 'close' method.

• The feature should be output AFTER assigning a value to the global variable. If the feature was output BEFORE assigning a value to the variable, its instance haven't been created yet when the feature arrived to the next PythonCaller.

In addition, if you save the dictionary into a feature attribute as a JSON document, it's not necessary to use a global variable. See @david_r's answer.

When you say global variable, you mean "global myDict" in the PythonCreator or in the startupPythonScript?

I thought that you needed to define the global variable in the PythonCreator since I found the declaration within your script. However global variables can be defined anywhere according to your requirement. All depends on what you want to do with scripting ;)