InvalidOperation: [<class 'decimal.ConversionSyntax'>] in Lambda function python

Question

I have a sentence with plain numbers and ordinal numbers and I wanted to convert ordinal digits to words like 2 nd to Second, 56 th to Fifty sixth. I used the library num2words and below code works perfectly.

import num2words
text = "ordinal numbers are like as 42 nd, 67 th, and 5 th and plain numbers such as 1, 2, 3."
numbers = re.findall('(\d+ )[st|nd|rd|th]', text)
numbers
for n in numbers:
    ordinalAsString = num2words.num2words(n, ordinal=True)
    print(ordinalAsString)
    #forty-second
    #sixty-seventh
    #fifth

Now I want to create a lambda function such that,

sentence = "ordinal numbers are like as 42 nd, 67 th, and 5 th and plain numbers such as 1, 2, 3."
o/p sentence = "ordinal numbers are like as fourty-second, sixty-seventh, and fifth and plain numbers such as 1, 2, 3."

I wrote the function like this,

sentence = re.sub(r"(\d+ )[st|nd|rd|th]", lambda x: num2words.num2words(str(x), ordinal=True), sentence)

But that throws an error like,

InvalidOperation: [<class 'decimal.ConversionSyntax'>]

What is wrong in the code?

Your regular expressions are different, is that the problem? — Jackson H
– Jackson H, Commented Nov 3, 2021 at 17:54
str(x) isn't going to give you the string you want; x.group(1) will. [st|nd|rd|th] also does not match what you think it does; it's equivalent to [st|ndrh], with the | acting as a literal character, not an alternation operator. — chepner
– chepner, Commented Nov 3, 2021 at 18:16
Yes, that's because the bracket expression isn't matching one of st, nd, rd, or th; it's matching one of s, t, |, n, d, r, or h. — chepner
– chepner, Commented Nov 3, 2021 at 18:25
Try (?:st|nd|rd|th). (st|nd|rd|th) would work as well, but no use making it a capture group if you don't need to use the captured suffix. — chepner
– chepner, Commented Nov 3, 2021 at 18:25

chepner · Accepted Answer · 2021-11-03 18:28:06Z

1

There are two problems:

Your regular expression isn't correctly matching the suffix, only the first letter of the suffix. [st|nd|rd|th] matches exactly one of the characters inside the brackets; duplicates are ignored, so it's equivalent to [st|ndrh], with the | treated as a character to match like each of the letters. Use r"(\d+ )(?:st|nd|rd|th)" instead; the | inside the non-capture group (?:...) does work to separate the 4 patterns st, nd, rd, and th.
The callable passed to re.sub takes a Match object as its argument. You need to use its group method to extract the captured sting. lambda x: num2words.num2words(x.group(1), ordinal=True).

answered Nov 3, 2021 at 18:28

chepner

538k77 gold badges594 silver badges746 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

adikh Over a year ago

yes, it worked. Thanks a ton. For explanation and answer.

Collectives™ on Stack Overflow

InvalidOperation: [<class 'decimal.ConversionSyntax'>] in Lambda function python

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related