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POURLs matching regexp very slow on some strings
 

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  1. POURLs matching regexp very slow on some strings
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    <p>Here is my regexp for finding URLs in some string (i need the group for the domain because further actions are based on the domain) and i noticed for some strings 'fffffffff' in this example it's very slow, there is something obvious i missing?</p> <pre><code>&gt;&gt;&gt; URL_ALLOWED = r"[a-z0-9$-_.+!*'(),%]" &gt;&gt;&gt; URL_RE = re.compile( ... r'(?:(?:https?|ftp):\/\/)?' # protocol ... r'(?:www.)?' # www ... r'(' # host - start ... r'(?:' ... r'[a-z0-9]' # first character of domain('-' not allowed) ... r'(?:' ... r'[a-z0-0-]*' # characters in the middle of domain ... r'[a-z0-9]' # last character of domain('-' not allowed) ... r')*' ... r'\.' # dot before next part of domain name ... r')+' ... r'[a-z]{2,10}' # TLD ... r'|' # OR ... r'(?:[0-9]{1,3}\.){3}[0-9]{1,3}' # IP address ... r')' # host - end ... r'(?::[0-9]+)?' # port ... r'(?:\/%(allowed_chars)s+/?)*' # path ... r'(?:\?(?:%(allowed_chars)s+=%(allowed_chars)s+&amp;)*' # GET params ... r'%(allowed_chars)s+=%(allowed_chars)s+)?' # last GET param ... r'(?:#[^\s]*)?' % { # anchor ... 'allowed_chars': URL_ALLOWED ... }, ... re.IGNORECASE ... ) &gt;&gt;&gt; from time import time &gt;&gt;&gt; strings = [ ... 'foo bar baz', ... 'blah blah blah blah blah blah', ... 'f' * 10, ... 'f' * 20, ... 'f' * 30, ... 'f' * 40, ... ] &gt;&gt;&gt; def t(): ... for string in strings: ... t1 = time() ... URL_RE.findall(string) ... print string, time() - t1 ... &gt;&gt;&gt; t() foo bar baz 3.91006469727e-05 blah blah blah blah blah blah 6.98566436768e-05 ffffffffff 0.000313997268677 ffffffffffffffffffff 0.183916091919 ffffffffffffffffffffffffffffff 178.445468903 </code></pre> <p>Yeah i know there is another solution to use very simple regexp (word that contain dots for example) and use urlparse later to get domain, but urlparse doesn't work as expected when we don't have protocol in URL:</p> <pre><code>&gt;&gt;&gt; urlparse('example.com') ParseResult(scheme='', netloc='', path='example.com', params='', query='', fragment='') &gt;&gt;&gt; urlparse('http://example.com') ParseResult(scheme='http', netloc='example.com', path='', params='', query='', fragment='') &gt;&gt;&gt; urlparse('example.com/test/test') ParseResult(scheme='', netloc='', path='example.com/test/test', params='', query='', fragment='') &gt;&gt;&gt; urlparse('http://example.com/test/test') ParseResult(scheme='http', netloc='example.com', path='/test/test', params='', query='', fragment='') &gt;&gt;&gt; urlparse('example.com:1234/test/test') ParseResult(scheme='example.com', netloc='', path='1234/test/test', params='', query='', fragment='') &gt;&gt;&gt; urlparse('http://example.com:1234/test/test') ParseResult(scheme='http', netloc='example.com:1234', path='/test/test', params='', query='', fragment='') </code></pre> <p>Yeah prepending http:// is also a solution(i'm still not 100% sure if there are no other urlparse issues) but i'm curious what's wrong with this regexp anyway</p>
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    1. USvirhilo
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      1. POURLs matching regexp very slow on some strings
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      1. VTUpMod
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      1. VTUpMod
    1. COThat regex makes my brain hurt
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      1. POURLs matching regexp very slow on some strings
      1. USchucksmash
    2. COMy gut feeling is that any search target with lots of h's or f's (or longer substrings) that match the start of the pattern in it will chug. Have you considered trying to preprocess the string by tokenizing delimted by whitepace, then running a simpler regex against those tokens? Trying to oneline things isn't always the fastest way.
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      1. USSilas Ray
    3. COurlparse there is working as expected. It's just that what you're passing it isn't a URL. "example.com" isn't a URL, and "myshellserver:22" isn't a URL either. You have to be prepared to accept that this approach will produce false positives sometimes, and if so, maybe the simple word-with-a-dot regex would be fine. Otherwise I agree with IamChuckB
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      1. POURLs matching regexp very slow on some strings
      1. USmoopet
 

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