正则表达式仅匹配粘在一起的大写单词（即不被空格分隔）

Question

I have a long list of strings which are all random words, all of them capitalized, such as 'Pomegranate' and 'Yellow Banana' . However, some of them are stuck together, like so: 'AppleOrange' . There are no special characters or digits.

What I need is a regular expression on Python that matches 'Apple' and 'Orange' separately, but not 'Pomegranate' or 'Yellow' .

As expected, I'm very new to this, and I've only managed to write r"(?<!\s)([AZ][az]*)" ... But that still matches 'Yellow' and 'Pomegranate' . How do I do this?

Answer 1

This work:

import re
from collections import deque

pattern = r'([A-Z]{2,}(?=[A-Z]|$)|[A-Z](?=[a-z]|$))'
chunks = deque(re.split(pattern, 'AppleOrange'))

result = []
while len(chunks):
  buf = chunks.popleft()
  if len(buf) == 0:
    continue
  if re.match(r'^[A-Z]$', buf) and len(chunks):
    buf += chunks.popleft()
  result.append(buf)

print(result)

Output:

['Apple', 'Orange']

Check the OP here

Answer 2

If they all start with an uppercase char and optional lowercase chars, you can make use of lookarounds and an alternation to match both variations

(?<=[a-z])[A-Z][a-z]*|[A-Z][a-z]*(?=[A-Z])

The pattern matches:

• (?<=[az]) Assert az to the left
• [AZ][az]* match AZ and optional chars az
• | or
• [AZ][az]* match AZ and optional chars az
• (?=[AZ]) Assert AZ to the right

Regex demo

Example

import re

pattern = r"(?<=[a-z])[A-Z][a-z]*|[A-Z][a-z]*(?=[A-Z])"
s = ("AppleOrange\nPomegranate Yellow Banana")

print(re.findall(pattern, s))

Output

['Apple', 'Orange']

---

Another option could be getting out of the way what you don't want by matching it, and use a capture group for what you want to keep and remove the empty entries from the result:

(?<!\S)[A-Z][a-z]*(?!\S)|([A-Z][a-z]*)

Regex demo | Python demo

import re

pattern = r"(?<!\S)[A-Z][a-z]*(?!\S)|([A-Z][a-z]*)"
s = ("AppleOrange\nPomegranate Yellow Banana")

print([x for x in re.findall(pattern, s) if x])