我的正则表达式错过了我要匹配的项目之一。 有什么我想念的吗？

Question

I have written this so far and it effectively captures 15 of the 16 students who got a 'B' grade. Unfortunately, the last student with a 'B' is left out. Is there something I am missing?

import re
def grades():
    with open ("assets/grades.txt", "r") as file:
        grades = file.read()
        #grades = re.findall(\w+\s\w+\:\s[B]\s+, grades)
        grades = re.findall("(?P<title>\w+\s\w+)(?=\:\s[B]\s+)",grades)
        print(grades)

Answer 1

Actually, you want to print all the line parts before : if the part after : is B .

So, you can achieve this without a regex:

def grades():
    with open ("assets/grades.txt", "r") as file:
        grades = []
        for line in file:
            parts = line.strip().split(':')
            if parts[1].strip() == 'B':
                grades.append(parts[0].strip())
        print(grades)

You may still get the list with the regex, using

import re
def grades():
    with open ("assets/grades.txt", "r") as file:
        grades = re.findall(r'^([^:\r\n]+):[^\S\r\n]*B$', file.read(), re.M)
        print(grades)

where ^([^:\r\n]+):[^\S\r\n]*B$ matches

• ^ - start of a line
• ([^:\r\n]+) - any zero or more chars other than : and CR/LF
• : - a colon
• [^\S\r\n]* - zero or more horizontal whitespace
• B - a B
• $ - end of a line.

See the regex demo .

See a Python demo :

file = """Ronald Mayr: A
Bell Kassulke: B
Alexander Zeller: C
Simon Loidl: B"""

def grades():
    grades = []
    for line in file.splitlines():
        parts = line.strip().split(':')
        if parts[1].strip() == 'B':
            grades.append(parts[0].strip())
    print(grades)

grades()
# => ['Bell Kassulke', 'Simon Loidl']

import re
print( re.findall(r'^([^:\r\n]+):[^\S\r\n]*B$', file, re.M) )
## => ['Bell Kassulke', 'Simon Loidl']