Python Regex用于忽略具有两个连续大写字母的句子

Question

I have a simple problem at hand to ignore the sentences that contain two or more consecutive capital letters and many more grammar rules .

Issue: By the definition the regex should not match the string 'This is something with two CAPS.' , but it does match.

Code:

''' Check if a given sentence conforms to given grammar rules

    $ Rules
        * Sentence must start with a Uppercase character (e.g. Noun/ I/ We/ He etc.)
        * Then lowercase character follows.
        * There must be spaces between words.
        * Then the sentence must end with a full stop(.) after a word.
        * Two continuous spaces are not allowed.
        * Two continuous upper case characters are not allowed.
        * However the sentence can end after an upper case character.
'''

import re


# Returns true if sentence follows these rules else returns false
def check_sentence(sentence):
    checker = re.compile(r"^((^(?![A-Z][A-Z]+))([A-Z][a-z]+)(\s\w+)+\.$)")
    return checker.match(sentence)

print(check_sentence('This is something with two CAPS.'))

Output:

<_sre.SRE_Match object; span=(0, 32), match='This is something with two CAPS.'>

Answer 1

It's probably easier to write your regex in the negative (find all sentences that are bad sentences) than it is in the positive.

checker = re.compile(r'([A-Z][A-Z]|[ ][ ]|^[a-z])')
check2 = re.compile(r'^[A-Z][a-z].* .*\.$')
return not checker.findall(sentence) and check2.findall(sentence)

Answer 2

Your negative lookahead is only applying to the beginning of the string being tested.

2nd Capturing Group (^(?![AZ][AZ]+))

^ asserts position at start of the string

Negative Lookahead (?![AZ][AZ]+)

"This will NOT fail."

"THIS will fail."