title: Regex python remove colons and underscores
body: <p>I have a method that cleans tweets that I got from online, however I want to modify it so it will keep colons and underscores. I read the <a href="https://docs.python.org/2/library/re.html" rel="nofollow noreferrer">documentation</a> for regex in python and it seems the re.sub method is first finding the pattern, then replacing it with blank spaces, in the "tweet" variable. I still do not quite understand the first part where it specifies the patterns to find I understand some basics like ^ is finding if something starts with something, I tried taking out the last part <code>(\w+:\/\/\S+)</code> entirely thinking that was where the colon was coming from, but it is still removing colons. Can someone explain what each 3 parts of the pattern finding part does?</p>
  
  <pre><code>' '.join(re.sub("(@[A-Za-z0-9]+)|([^0-9A-Za-z \t])|(\w+:\/\/\S+)", " ", tweet).split())
  </code></pre>