正则表达式获取单词，如果它在中间有字符但在开头或结尾没有

Question

I have this code that successfully checks if a string has a character in the middle of the string but not in the beginning or in the end. My regex though return all the string that have the character in the beginning or in the end and then I just collect all the results that the regex wont return which is counter intuitive. So my regex detects all the words that start or end with a specific character while I want a regex that detects all the words that have a specific character in the middle but not in the beginning or in the end.

This is my code:

def getCharInMiddle():
    # with open("assets/grades.txt", "r") as file:
    #     grades = file.read()

    content = ["bDa", "MariaBkB", "DimAb", "OL gaBd"]
    pattern = "[a-zA-Z]*[bB][a-zA-Z]*"

    for entry in content:

        print(entry)
        result = re.match(pattern, entry)
        if not result:
            print("\n ----> " + entry + "\n")

Is there a regex that would check if an entry has the character in the middle but it does not have it in the beginning or end?

---

Update

I updated the `pattern' to be:

pattern = "\b(?![bB])[a-zA-Z]+[bB][a-zA-Z]+(?<![bB])\b"

but then no entry is matched

Answer 1

You can try with this pattern

^(?![bB]).*[bB].*(?<![bB])$

It matches the strings which contains b or B, but don't start or finish with those 2 characters.

Answer 2

You can use

re.findall(r'\b(?!b[a-z]+b\b)[a-z]+b[a-z]+\b', text, re.I)          # ASCII only letters
re.findall(r'\b(?!b[^\W\d_]+b\b)[^\W\d_]+b[^\W\d_]+\b', text, re.I) # Any Unicode letters

See the regex demo . Note the use of the case insensitive modifier.

Details :

• \b - a word boundary
• (?!b[^\W\d_]+b\b) - not followed with b , then one or more letters and then a b followed with a word boundary
• [^\W\d_]+ - one or more letters
• b - a b
• [^\W\d_]+ - one or more letters
• \b - a word boundary.

See the Python demo :

import re
content = ["bDa", "MariaBkB", "DimAb", "OL gaBd"]
pattern = re.compile(r'\b(?!b[^\W\d_]+b\b)[^\W\d_]+b[^\W\d_]+\b', re.I)
for s in content:
  print(  pattern.findall(s) )
# => [], ['MariaBkB'], [], ['gaBd']

Answer 3

This here may help you:

\b[^bB]\w+[bB]\w+[^bB]\b


\b - boundary
[^bB] - cannot be those letters
\w+ - all word characters (at least one)
[bB] - b or B in the middle
\w+ - all word characters (at least one)
[^bB] - cannot be those letters
\b - boundary