regex - match words with hyphen only uppercase

Question

I'm trying to match words that have more than 1 letter and: are all-upercase, first letter lowercase and following letters uppercase, or containing a hyphen in the middle ONLY if all the letters are uppercase. This is my code:

s = "ASCII, aSCII, AS-CII, AS-cii"

myset =   set(re.findall(r"\b[a-z]?[A-Z]+\-?[A-Z]{1,}",s))

Out[555]: {'AS', 'AS-CII', 'ASCII', 'aSCII'}

As you can see, the "AS" shouldn't be returned because it contains lower case letters after the hyphen. How could I fix this?

Tried this but the result is an error:

myset = set(re.findall(r"\b[a-z]?[A-Z]+\-?[A-Z]+{1,}",s))

  File "<ipython-input-545-7bdc0c902553>"
    myset = set(re.findall(r"\b[a-z]?[A-Z]+\-?[A-Z]+{1,}",s))

  File "/home/c1962135/.local/share/virtualenvs/c1962135-9R_1M4TP/lib/python3.6/re.py", line 222, in findall
    return _compile(pattern, flags).findall(string)

  File "/home/c1962135/.local/share/virtualenvs/c1962135-9R_1M4TP/lib/python3.6/re.py", line 301, in _compile
    p = sre_compile.compile(pattern, flags)

  File "/home/c1962135/.local/share/virtualenvs/c1962135-9R_1M4TP/lib/python3.6/sre_compile.py", line 562, in compile
    p = sre_parse.parse(p, flags)

  File "/home/c1962135/.local/share/virtualenvs/c1962135-9R_1M4TP/lib/python3.6/sre_parse.py", line 855, in parse
    p = _parse_sub(source, pattern, flags & SRE_FLAG_VERBOSE, 0)

  File "/home/c1962135/.local/share/virtualenvs/c1962135-9R_1M4TP/lib/python3.6/sre_parse.py", line 416, in _parse_sub
    not nested and not items))

  File "/home/c1962135/.local/share/virtualenvs/c1962135-9R_1M4TP/lib/python3.6/sre_parse.py", line 619, in _parse
    source.tell() - here + len(this))

error: multiple repeat

Answer 1

Here we are

res = [x[0] for x in re.findall(r"(([a-z]{1}[A-Z]+)|([A-Z]+\-[A-Z]+))",s)]
print(res)
print(set(res))

gives

['aSCII', 'AS-CII']

Tell me. I splitted to add OR logic with | between.

Answer 2

You could use a conditional expression :

(...)?(if true than this|else this)

For your case, this could be

\b([a-z])?(?(1)[A-Z]+|[-A-Z]+[A-Z])(?!-)\b

See a demo on regex101.com .

---

Broken down this reads

\b # a word boundary ([az])? # match a lower case letter if it is there (?(1) # if the lower case letter is there, match this branch [AZ]+ | [-AZ]+[AZ] # else this one ) (?,-)\b # do not break at a -, followed by another boundary

Answer 3

The following regex matches all of the mentioned critera:

\b[a-z]*[A-Z]+[\-A-Z]+[A-Z]+\b

Please check here https://regex101.com/r/JNC4kN/1/

But this will fail if you give this type of example like aTH-THTH (small letter following hyphen and uppercase). If you want only UPPER-UPPER then follow this regex:

\b[a-z]{0,1}(?<!\-)[A-Z]+\b(?!\-)|\b[A-Z]+\-[A-Z]+\b

check here

Answer 4

You could use the following regular expression, which covers edge cases having to do with the word preceded by or followed by a hyphen (as shown at the link below):

(?<!\w|(?<=\w)-)(?:[a-zA-Z][A-Z]+|[A-Z]{2,}|[A-Z]+-[A-Z]+)(?!\w|-(?=\w))

Demo

Python's regex engine performs the following operations.

(?<!              # begin a negative lookbehind
  \w              # match word char
  |               # or
  (?<=\w)         # match a word char in a positive lookbehind
  -               # match '-'
)                 # end negative lookbehind
(?:               # begin non-cap grp
  [a-zA-Z][A-Z]+  # match a lc letter then 1+ uc letters
  |               # or
  [A-Z]{2,}       # match 2+ uc letters
  |               # or
  [A-Z]+-[A-Z]+   # match 1+ uc letters, '-', then 1+ uc letters
)                 # end non-cap grp
(?!               # begin negative lookahead
  \w              # match word char
  |               # or
  -               # match '-'
  (?=\w)          # match a word char in a positive lookahead
)                 # end negative lookahead