MissingPartSpecialGroup.qhelp

<!DOCTYPE qhelp PUBLIC
  "-//Semmle//qhelp//EN"
  "qhelp.dtd">
<qhelp>
<overview>
<p>
One of the problems with using regular expressions is that almost any sequence of characters is a valid pattern.
This means that it is easy to omit a necessary character and still have a valid regular expression.
Omitting a character in a named capturing group is a specific case which can dramatically change the meaning of a regular expression.
</p>

</overview>
<recommendation>

<p>
Examine the regular expression to find and correct any typos.
</p>

</recommendation>
<example>
<p>
In the following example, the regular expression for <code>matcher</code>, <code>r"(P&lt;name&gt;[\w]+)"</code>, is missing a "?" and will
match only strings of letters that start with "P&lt;name&gt;", instead of matching any sequence of letters
and placing the result in a named group.
The fixed version, <code>fixed_matcher</code>, includes the "?" and will work as expected.
</p>

<sample src="MissingPartSpecialGroup.py" />

</example>
<references>

<li>Python Standard Library: <a href="https://docs.python.org/library/re.html">Regular expression operations</a>.</li>
<li>Regular-Expressions.info: <a href="http://www.regular-expressions.info/named.html">Named Capturing Groups</a>.</li>

</references>
</qhelp>