# Example of custom components

**URL:** <https://forum.rasa.com/t/example-of-custom-components/2706>\
**Category:** Getting Started with Rasa\
**Created:** [November 15, 2018, 3:14pm UTC](https://forum.rasa.com/t/example-of-custom-components/2706 "2018-11-15T15:14:12Z")\
**Posts on this page:** 6\
**Page:** 1

<div class="post-metadata">

**Author:** ![huberrom](https://dub1.discourse-cdn.com/flex013/user_avatar/forum.rasa.com/huberrom/32/1209_2.png) [@huberrom](https://forum.rasa.com/u/huberrom)\
**Post date:** [November 15, 2018, 3:14pm UTC](https://forum.rasa.com/t/example-of-custom-components/2706/1 "2018-11-15T15:14:12Z")

</div>

Hi everyone, I want to add a spell checking component in my nlu pipeline. I saw the template for custom components, but I didn’t find an full example of how to implement a custom component. If anyone has a full example from a blog / personnal project, I’ll be gratefull. You can delete all the treatment, I just want to see the default configuration and where I can process the message (I know it’s in the process method, but how do I return the message after the treatment ?)

A quick explanation would be very helpful too !

---

<div class="post-metadata">

**Author:** ![favarete](https://dub1.discourse-cdn.com/flex013/user_avatar/forum.rasa.com/favarete/32/3854_2.png) [@favarete](https://forum.rasa.com/u/favarete)\
**Post date:** [July 9, 2019, 11:40pm UTC](https://forum.rasa.com/t/example-of-custom-components/2706/2 "2019-07-09T23:40:09Z")

</div>

Hey, @huberrom. I’m also interested in this. Did you found a solution? I’m stuck in this for my project and, based on other similar questions here in the forum, I’ll also be ignored if I open another question about this 😕

---

<div class="post-metadata">

**Author:** ![gcgloven](https://dub1.discourse-cdn.com/flex013/user_avatar/forum.rasa.com/gcgloven/32/3915_2.png) [@gcgloven](https://forum.rasa.com/u/gcgloven)\
**Post date:** [July 10, 2019, 2:18am UTC](https://forum.rasa.com/t/example-of-custom-components/2706/3 "2019-07-10T02:18:00Z")

</div>

You may find a reference of Sentiment Analyzer here: [Enhancing Rasa NLU models with Custom Components - Rasa Blog - Medium](https://medium.com/rasa-blog/enhancing-rasa-nlu-models-with-custom-components-6f54040c4a77)

---

<div class="post-metadata">

**Author:** ![favarete](https://dub1.discourse-cdn.com/flex013/user_avatar/forum.rasa.com/favarete/32/3854_2.png) [@favarete](https://forum.rasa.com/u/favarete)\
**Post date:** [July 10, 2019, 1:30pm UTC](https://forum.rasa.com/t/example-of-custom-components/2706/4 "2019-07-10T13:30:27Z")

</div>

I saw this post, but I can’t figure out how to apply the example to this specific case of spell checking. I’ll open another question, maybe explain my problem here will be out of this specific topic a little.

---

<div class="post-metadata">

**Author:** ![huberrom](https://dub1.discourse-cdn.com/flex013/user_avatar/forum.rasa.com/huberrom/32/1209_2.png) [@huberrom](https://forum.rasa.com/u/huberrom)\
**Post date:** [July 10, 2019, 2:42pm UTC](https://forum.rasa.com/t/example-of-custom-components/2706/5 "2019-07-10T14:42:28Z")

</div>

Hey, sorry I stopped working on rasa a while ago, but here is a quick example (can’t give you the full code)

```
from symspellpy.symspellpy import SymSpell

ROOT_DIR = os.path.dirname(os.path.abspath( __file__ ))
DICTIONARIES_PATH = os.path.join(ROOT_DIR, 'dictionaries/')

class SpellCheck(Component):
""" Component put at the start of the pipeline to spell check the user message."""

name = "SpellChecking"

# Defines what language(s) this component can handle.
language_list = "fr"

# Defines the default configuration parameters of a component
# these values can be overwritten in the pipeline configuration
# of the model.
defaults = {
    "initial_capacity": 83000,
    # maximum edit distance per dictionary precalculation (max_edit_distance_lookup <= max_edit_distance_dictionary)
    "max_edit_distance_dictionary": 2,
    "prefix_length": 7,
    # max edit distance per lookup (per single word, not per whole input string),
    "max_edit_distance_lookup": 2,
    "dictionary": "fr_dictionary.txt"
}

def __init__ (self, component_config=None):
    super(SpellCheck, self). __init__ (component_config)
    logging.basicConfig(level='DEBUG')
    self.sym_spell = SymSpell(self.component_config["initial_capacity"],
                              self.component_config["max_edit_distance_dictionary"],
                              self.component_config["prefix_length"])
    self.load_sym_spell(self.component_config["dictionary"])

def process(self, message, **kwargs):
    # For the moment, if the dictionary is not loaded, we skip the spell checking
    if self.sym_spell is None:
        logger.info("Skip spell check because dictionary failed to load")
        return
    # Get and split by numbers
    numbers = re.findall(r"\d*[\.|\,]\d+|\d+", message.text)
    split = re.split(r"\d*[\.|\,]\d+|\d+", message.text)

    correction = ""
    while i < len(split):
        suggestions = self.sym_spell.lookup_compound(split[i],
                                                     self.component_config["max_edit_distance_lookup"])
        correction += suggestions[0].term
        i += 1

    # Split is use here to remove useless space
    correction = " ".join(correction.split())
    logger.info("Correction from %s to %s", message.text, correction)
    message.text = correction

def load_sym_spell(self, dictionary):
    # load dictionary
    dictionary_path = os.path.join(DICTIONARIES_PATH, dictionary)
    # column of the term in the dictionary text file
    term_index = 0
    # column of the term frequency in the dictionary text file
    count_index = 1
    if not self.sym_spell.load_dictionary(dictionary_path, term_index, count_index):
        logger.error("Unable to load spell dictionary")
        self.sym_spell = None

```

So as you can see, I used a library named “sym\_spell” ([GitHub - mammothb/symspellpy: Python port of SymSpell](https://github.com/mammothb/symspellpy)). Just have to import the dictionnary (which is a list of word + frequency, for example “a 155105”), easy to find in english, harder for other langages.

I do not understand all params sorry, and the corrector is not perfect but it’s doing its job. Small part in the code where I split the message with number, because the corrector is deleting them.

Once you have create your component, you just have to add it in your pipeline like that :

```
language: "fr"

pipeline:
- name: "spell_check_component.SpellCheck"
- name: "nlp_spacy"
- name: "tokenizer_whitespace"
- name: "ner_crf"
- name: "ner_synonyms"
- name: "intent_featurizer_count_vectors"
- name: "intent_classifier_tensorflow_embedding"
"epochs": 3000 

```

(The component SpellCheck is in the spell\_check\_component folder)

Hope it helps !

---

<div class="post-metadata">

**Author:** ![favarete](https://dub1.discourse-cdn.com/flex013/user_avatar/forum.rasa.com/favarete/32/3854_2.png) [@favarete](https://forum.rasa.com/u/favarete)\
**Post date:** [July 10, 2019, 2:50pm UTC](https://forum.rasa.com/t/example-of-custom-components/2706/6 "2019-07-10T14:50:03Z")

</div>

Great!! Thank you very much! I think I know the problem in my code now 😀