Trouble with a very simple regex

Question

I am using python to try to write some simple code that looks through strings with regular expressions and finds things. In this string:

and the next nothing is 44827

I want my regex to return just the numbers.

I have set up my python program like this:

buf = "and the next nothing is 44827"
number = re.search("[0-9]*", buf)
print buf
print number.group()

What number.group() returns is an empty string. However, when the regex is:

number = re.search("[0-9]+", buf)

The full number (44827) is properly extracted. What am I missing here?

Answer 1

The problem is that [0-9]* matches zero or more digits, so it is more than happy to match to a zero-length string.

Meanwhile, [0-9]+ matches one or more digits, so it needs to see at least one number in order to catch.

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you might want to use findall and handle the case in which you have multiple numbers per line.