Python Regex not returning

Question

I have a function that should return a certain number from a mysql table. The number is filtered out of the string using regex like so: ^$(\d*),$$. The original string is (36,) and the regex should change it to this: 36. But i still get (36,)!

class db:
    con = mysql.connect()
    cur = con.cursor()

def fo(self, query):
    self.cur.execute(query)
    return re.search('^\((\d*),\)$', 
    str(self.cur.fetchone())).group(0)

and further on I call the function:

return db().fo('SELECT id FROM `GIP-Schema`.user WHERE name = \'{0}\''.format(name))

@juanpa.arrivillaga I don't understand what you mean, it's the value that the regex is used on, if that wouldn't work, there would be no point in regex, right? — Thom Ernst
– Thom Ernst, Commented May 13, 2017 at 20:03

Wiktor Stribiżew · Accepted Answer · 2017-05-13 20:01:49Z

3

You need to get Group 1 contents because ^$(\d*),$$ pattern matches ( at the start of the string, than captures into Group 1 zero or more digits (I suggest to capture one or more digits), and then matches ,) at the end of the string. Also, it is a good idea to first check if a match was found:

def fo(self, query):
    self.cur.execute(query)
    m = re.search('^\((\d+),\)$', str(self.cur.fetchone()))
    res = ''
    if m:
        res = m.group(1)
    return res

See the regex demo

answered May 13, 2017 at 20:01

Wiktor Stribiżew

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Thom Ernst · Accepted Answer · 2017-05-13 19:59:53Z

1

Thanks to Wiktor for pointing it out, apparently your first group is a 1, not a 0 .group(0) -> .group(1)

answered May 13, 2017 at 19:59

Thom Ernst

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