使用RegEx查找1个字母和2个数字

Question

I have been writing a program recently and a part of it requires me to get information form inside a string. I need to find where there is 1 letter immediately followed by 2 numbers (eg S07) and I can't work out the RegEx for it.

def get_season(filenames):
    pattern = "^[a-zA-z]{1}[\d]{2}$"
    found = re.search(filenames[0], pattern)
    season_name = found.string
    season = season_name[1:3]
    print(season)

I know that this information is in the string but it keeps giving me "None" in response

(I'm not too sure if the code section has formatted correctly, in the preview it shows as on the same line, but the indentation in my program is correct)

Answer 1

You swapped the arguments to re.search() . The first argument is the pattern, not the string to match:

found = re.search(pattern, filenames[0])

Your pattern is also overly wide; Az matches everything between Z (uppercase) and a (lowercase) too. The correct pattern is:

pattern = "^[a-zA-Z]\d{2}$"

where {1} is the default, so I omitted that.

If you are matching this against filenames, you probably do not want to use the start or end anchors, that would limit matches to exact strings only:

>>> re.search("^[a-zA-Z]\d{2}$", "S07").string
'S20'
>>> re.search("^[a-zA-Z]\d{2}$", "S07E01 - Meet the New Boss.avi") is None
True
>>> re.search("^[a-zA-Z]\d{2}$", "S07E01 - Meet the New Boss.avi") is None
True
>>> re.search("[a-zA-Z]\d{2}", "S07E01 - Meet the New Boss.avi").string
'S07E01 - Meet the New Boss.avi'

And you want to use .group() to get the matched portion, not string (which is the original input string):

>>> re.search("[a-zA-Z]\d{2}", "S07E01 - Meet the New Boss.avi").group()
'S07'

If you only wanted the numbers , you need to add a group, and pick that. You create a capturing group with parenthesis:

>>> re.search("[a-zA-Z](\d{2})", "S07E01 - Meet the New Boss.avi").group(1)
'07'

This selects the first group ( .group(1) ), which is the parenthesis around the 2 digits portion.

Answer 2

Your regex will catch only the string which consits only of one letter and two digits, to check whole string for multiple occurences use these:

Try this regex:

[a-zA-Z]\d{2}

INPUT

asdasdasS01asfasfsa

OUTPUT

S01

If you want to find a word wich consists only of a letter followed by two digits use this regex:

\b[a-zA-Z]\d{2}\b

Only numebers capture regex:

[a-zA-Z](\d{2})

INPUT

asdasdasS01asfasfsa

OUTPUT

01

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Also swap the arguments in serach method.