spacy IS_DIGIT or LIKE_NUM not working as expected for certain chars - spacy

Question

I am trying to extract some numbers using IS_DIGIT and LIKE_NUM attributes but it seems to be behaving a bit strange for a beginner like me.
The matcher is only able to detect the numbers when the 5 character string ends in M, G, T . If it is any other character, the IS_DIGIT and LIKE_NUM attributes are not able to detect. What am I missing here?
nlp = spacy.load("en_core_web_sm")
matcher = Matcher(nlp.vocab)
pattern = [{'LIKE_NUM': True}]
matcher.add("DIGIT",[pattern])
doc = nlp("1231M 1232G 1233H 1234J 1235V 1236T")
matches = matcher(doc, as_spans=True)
for span in matches:
print(span.text, span.label_)
# prints only 1231, 1232 and 1236

Answer 1

It may be helpful to just check which tokens are true for LIKE_NUM, like this:
import spacy
from spacy.matcher import Matcher
nlp = spacy.load("en_core_web_sm")
matcher = Matcher(nlp.vocab)
pattern = [{"LIKE_NUM": True}]
matcher.add("DIGIT", [pattern])
doc = nlp("1231M 1232G 1233H 1234J 1235V 1236T")
for tok in doc:
print(tok, tok.like_num)
Here you'll see that sometimes the tokens you have are split in two, and sometimes they aren't. The tokens you match are only the ones that consist just of digits.
Now, why are M, G, and T split off, while H, J, and V aren't? This is because they are units, as for mega, giga, or terabytes.
This behaviour with units may seem inconsistent and weird, but it's been chosen to be consistent with the training data used for the English models. If you need to change it for your application, look at this section in the docs, which covers customizing the exceptions.