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<title>7.6. Case study: Parsing Phone Numbers</title>
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<h2 class="title"><a name="re.phone"></a>7.6. Case study: Parsing Phone Numbers
</h2>
</div>
</div>
<div></div>
</div>
<div class="abstract">
<p>So far you've concentrated on matching whole patterns. Either the pattern matches, or it doesn't. But regular expressions
are much more powerful than that. When a regular expression <span class="emphasis"><em>does</em></span> match, you can pick out specific pieces of it. You can find out what matched where.
</p>
</div>
<p>This example came from another real-world problem I encountered, again from a previous day job. The problem: parsing an American
phone number. The client wanted to be able to enter the number free-form (in a single field), but then wanted to store the
area code, trunk, number, and optionally an extension separately in the company's database. I scoured the Web and found many
examples of regular expressions that purported to do this, but none of them were permissive enough.
</p>
<p>Here are the phone numbers I needed to be able to accept:</p>
<div class="itemizedlist">
<ul>
<li><tt class="literal">800-555-1212</tt></li>
<li><tt class="literal">800 555 1212</tt></li>
<li><tt class="literal">800.555.1212</tt></li>
<li><tt class="literal">(800) 555-1212</tt></li>
<li><tt class="literal">1-800-555-1212</tt></li>
<li><tt class="literal">800-555-1212-1234</tt></li>
<li><tt class="literal">800-555-1212x1234</tt></li>
<li><tt class="literal">800-555-1212 ext. 1234</tt></li>
<li><tt class="literal">work 1-(800) 555.1212 #1234</tt></li>
</ul>
</div>
<p>Quite a variety! In each of these cases, I need to know that the area code was <tt class="literal">800</tt>, the trunk was <tt class="literal">555</tt>, and the rest of the phone number was <tt class="literal">1212</tt>. For those with an extension, I need to know that the extension was <tt class="literal">1234</tt>.
</p>
<p>Let's work through developing a solution for phone number parsing. This example shows the first step.</p>
<div class="example"><a name="re.phone.example"></a><h3 class="title">Example 7.10. Finding Numbers</h3><pre class="screen">
<tt class="prompt">>>> </tt><span class="userinput">phonePattern = re.compile(r<span class='pystring'>'^(\d{3})-(\d{3})-(\d{4})$'</span>)</span> <a name="re.phone.1.1"></a><img src="../images/callouts/1.png" alt="1" border="0" width="12" height="12">
<tt class="prompt">>>> </tt><span class="userinput">phonePattern.search(<span class='pystring'>'800-555-1212'</span>).groups()</span> <a name="re.phone.1.2"></a><img src="../images/callouts/2.png" alt="2" border="0" width="12" height="12">
<span class="computeroutput">('800', '555', '1212')</span>
<tt class="prompt">>>> </tt><span class="userinput">phonePattern.search(<span class='pystring'>'800-555-1212-1234'</span>)</span> <a name="re.phone.1.3"></a><img src="../images/callouts/3.png" alt="3" border="0" width="12" height="12">
<tt class="prompt">>>> </tt>
</pre><div class="calloutlist">
<table border="0" summary="Callout list">
<tr>
<td width="12" valign="top" align="left"><a href="#re.phone.1.1"><img src="../images/callouts/1.png" alt="1" border="0" width="12" height="12"></a>
</td>
<td valign="top" align="left">Always read regular expressions from left to right. This one matches the beginning of the string, and then <tt class="literal">(\d{3})</tt>. What's <tt class="literal">\d{3}</tt>? Well, the <tt class="literal">{3}</tt> means “<span class="quote">match exactly three numeric digits</span>”; it's a variation on the <a href="n_m_syntax.html" title="7.4. Using the {n,m} Syntax"><tt class="literal">{n,m} syntax</tt></a> you saw earlier. <tt class="literal">\d</tt> means “<span class="quote">any numeric digit</span>” (<tt class="literal">0</tt> through <tt class="literal">9</tt>). Putting it in parentheses means “<span class="quote">match exactly three numeric digits, <span class="emphasis"><em>and then remember them as a group that I can ask for later</em></span></span>”. Then match a literal hyphen. Then match another group of exactly three digits. Then another literal hyphen. Then another
group of exactly four digits. Then match the end of the string.
</td>
</tr>
<tr>
<td width="12" valign="top" align="left"><a href="#re.phone.1.2"><img src="../images/callouts/2.png" alt="2" border="0" width="12" height="12"></a>
</td>
<td valign="top" align="left">To get access to the groups that the regular expression parser remembered along the way, use the <tt class="function">groups()</tt> method on the object that the <tt class="function">search</tt> function returns. It will return a tuple of however many groups were defined in the regular expression. In this case, you
defined three groups, one with three digits, one with three digits, and one with four digits.
</td>
</tr>
<tr>
<td width="12" valign="top" align="left"><a href="#re.phone.1.3"><img src="../images/callouts/3.png" alt="3" border="0" width="12" height="12"></a>
</td>
<td valign="top" align="left">This regular expression is not the final answer, because it doesn't handle a phone number with an extension on the end. For
that, you'll need to expand the regular expression.
</td>
</tr>
</table>
</div>
</div>
<div class="example"><a name="d0e19043"></a><h3 class="title">Example 7.11. Finding the Extension</h3><pre class="screen">
<tt class="prompt">>>> </tt><span class="userinput">phonePattern = re.compile(r<span class='pystring'>'^(\d{3})-(\d{3})-(\d{4})-(\d+)$'</span>)</span> <a name="re.phone.2.1"></a><img src="../images/callouts/1.png" alt="1" border="0" width="12" height="12">
<tt class="prompt">>>> </tt><span class="userinput">phonePattern.search(<span class='pystring'>'800-555-1212-1234'</span>).groups()</span> <a name="re.phone.2.2"></a><img src="../images/callouts/2.png" alt="2" border="0" width="12" height="12">
<span class="computeroutput">('800', '555', '1212', '1234')</span>
<tt class="prompt">>>> </tt><span class="userinput">phonePattern.search(<span class='pystring'>'800 555 1212 1234'</span>)</span> <a name="re.phone.2.3"></a><img src="../images/callouts/3.png" alt="3" border="0" width="12" height="12">
<tt class="prompt">>>> </tt>
<tt class="prompt">>>> </tt><span class="userinput">phonePattern.search(<span class='pystring'>'800-555-1212'</span>)</span> <a name="re.phone.2.4"></a><img src="../images/callouts/4.png" alt="4" border="0" width="12" height="12">
<tt class="prompt">>>> </tt>
</pre><div class="calloutlist">
<table border="0" summary="Callout list">
<tr>
<td width="12" valign="top" align="left"><a href="#re.phone.2.1"><img src="../images/callouts/1.png" alt="1" border="0" width="12" height="12"></a>
</td>
<td valign="top" align="left">This regular expression is almost identical to the previous one. Just as before, you match the beginning of the string, then
a remembered group of three digits, then a hyphen, then a remembered group of three digits, then a hyphen, then a remembered
group of four digits. What's new is that you then match another hyphen, and a remembered group of one or more digits, then
the end of the string.
</td>
</tr>
<tr>
<td width="12" valign="top" align="left"><a href="#re.phone.2.2"><img src="../images/callouts/2.png" alt="2" border="0" width="12" height="12"></a>
</td>
<td valign="top" align="left">The <tt class="function">groups()</tt> method now returns a tuple of four elements, since the regular expression now defines four groups to remember.
</td>
</tr>
<tr>
<td width="12" valign="top" align="left"><a href="#re.phone.2.3"><img src="../images/callouts/3.png" alt="3" border="0" width="12" height="12"></a>
</td>
<td valign="top" align="left">Unfortunately, this regular expression is not the final answer either, because it assumes that the different parts of the
phone number are separated by hyphens. What if they're separated by spaces, or commas, or dots? You need a more general
solution to match several different types of separators.
</td>
</tr>
<tr>
<td width="12" valign="top" align="left"><a href="#re.phone.2.4"><img src="../images/callouts/4.png" alt="4" border="0" width="12" height="12"></a>
</td>
<td valign="top" align="left">Oops! Not only does this regular expression not do everything you want, it's actually a step backwards, because now you can't
parse phone numbers <span class="emphasis"><em>without</em></span> an extension. That's not what you wanted at all; if the extension is there, you want to know what it is, but if it's not
there, you still want to know what the different parts of the main number are.
</td>
</tr>
</table>
</div>
</div>
<p>The next example shows the regular expression to handle separators between the different parts of the phone number.</p>
<div class="example"><a name="d0e19106"></a><h3 class="title">Example 7.12. Handling Different Separators</h3><pre class="screen">
<tt class="prompt">>>> </tt><span class="userinput">phonePattern = re.compile(r<span class='pystring'>'^(\d{3})\D+(\d{3})\D+(\d{4})\D+(\d+)$'</span>)</span> <a name="re.phone.3.1"></a><img src="../images/callouts/1.png" alt="1" border="0" width="12" height="12">
<tt class="prompt">>>> </tt><span class="userinput">phonePattern.search(<span class='pystring'>'800 555 1212 1234'</span>).groups()</span> <a name="re.phone.3.2"></a><img src="../images/callouts/2.png" alt="2" border="0" width="12" height="12">
<span class="computeroutput">('800', '555', '1212', '1234')</span>
<tt class="prompt">>>> </tt><span class="userinput">phonePattern.search(<span class='pystring'>'800-555-1212-1234'</span>).groups()</span> <a name="re.phone.3.3"></a><img src="../images/callouts/3.png" alt="3" border="0" width="12" height="12">
<span class="computeroutput">('800', '555', '1212', '1234')</span>
<tt class="prompt">>>> </tt><span class="userinput">phonePattern.search(<span class='pystring'>'80055512121234'</span>)</span> <a name="re.phone.3.4"></a><img src="../images/callouts/4.png" alt="4" border="0" width="12" height="12">
<tt class="prompt">>>> </tt>
<tt class="prompt">>>> </tt><span class="userinput">phonePattern.search(<span class='pystring'>'800-555-1212'</span>)</span> <a name="re.phone.3.5"></a><img src="../images/callouts/5.png" alt="5" border="0" width="12" height="12">
<tt class="prompt">>>> </tt>
</pre><div class="calloutlist">
<table border="0" summary="Callout list">
<tr>
<td width="12" valign="top" align="left"><a href="#re.phone.3.1"><img src="../images/callouts/1.png" alt="1" border="0" width="12" height="12"></a>
</td>
<td valign="top" align="left">Hang on to your hat. You're matching the beginning of the string, then a group of three digits, then <tt class="literal">\D+</tt>. What the heck is that? Well, <tt class="literal">\D</tt> matches any character <span class="emphasis"><em>except</em></span> a numeric digit, and <tt class="literal">+</tt> means “<span class="quote">1 or more</span>”. So <tt class="literal">\D+</tt> matches one or more characters that are not digits. This is what you're using instead of a literal hyphen, to try to match
different separators.
</td>
</tr>
<tr>
<td width="12" valign="top" align="left"><a href="#re.phone.3.2"><img src="../images/callouts/2.png" alt="2" border="0" width="12" height="12"></a>
</td>
<td valign="top" align="left">Using <tt class="literal">\D+</tt> instead of <tt class="literal">-</tt> means you can now match phone numbers where the parts are separated by spaces instead of hyphens.
</td>
</tr>
<tr>
<td width="12" valign="top" align="left"><a href="#re.phone.3.3"><img src="../images/callouts/3.png" alt="3" border="0" width="12" height="12"></a>
</td>
<td valign="top" align="left">Of course, phone numbers separated by hyphens still work too.</td>
</tr>
<tr>
<td width="12" valign="top" align="left"><a href="#re.phone.3.4"><img src="../images/callouts/4.png" alt="4" border="0" width="12" height="12"></a>
</td>
<td valign="top" align="left">Unfortunately, this is still not the final answer, because it assumes that there is a separator at all. What if the phone
number is entered without any spaces or hyphens at all?
</td>
</tr>
<tr>
<td width="12" valign="top" align="left"><a href="#re.phone.3.4"><img src="../images/callouts/4.png" alt="4" border="0" width="12" height="12"></a>
</td>
<td valign="top" align="left">Oops! This still hasn't fixed the problem of requiring extensions. Now you have two problems, but you can solve both of
them with the same technique.
</td>
</tr>
</table>
</div>
</div>
<p>The next example shows the regular expression for handling phone numbers <span class="emphasis"><em>without</em></span> separators.
</p>
<div class="example"><a name="d0e19203"></a><h3 class="title">Example 7.13. Handling Numbers Without Separators</h3><pre class="screen">
<tt class="prompt">>>> </tt><span class="userinput">phonePattern = re.compile(r<span class='pystring'>'^(\d{3})\D*(\d{3})\D*(\d{4})\D*(\d*)$'</span>)</span> <a name="re.phone.4.1"></a><img src="../images/callouts/1.png" alt="1" border="0" width="12" height="12">
<tt class="prompt">>>> </tt><span class="userinput">phonePattern.search(<span class='pystring'>'80055512121234'</span>).groups()</span> <a name="re.phone.4.2"></a><img src="../images/callouts/2.png" alt="2" border="0" width="12" height="12">
<span class="computeroutput">('800', '555', '1212', '1234')</span>
<tt class="prompt">>>> </tt><span class="userinput">phonePattern.search(<span class='pystring'>'800.555.1212 x1234'</span>).groups()</span> <a name="re.phone.4.3"></a><img src="../images/callouts/3.png" alt="3" border="0" width="12" height="12">
<span class="computeroutput">('800', '555', '1212', '1234')</span>
<tt class="prompt">>>> </tt><span class="userinput">phonePattern.search(<span class='pystring'>'800-555-1212'</span>).groups()</span> <a name="re.phone.4.4"></a><img src="../images/callouts/4.png" alt="4" border="0" width="12" height="12">
<span class="computeroutput">('800', '555', '1212', '')</span>
<tt class="prompt">>>> </tt><span class="userinput">phonePattern.search(<span class='pystring'>'(800)5551212 x1234'</span>)</span> <a name="re.phone.4.5"></a><img src="../images/callouts/5.png" alt="5" border="0" width="12" height="12">
<tt class="prompt">>>> </tt>
</pre><div class="calloutlist">
<table border="0" summary="Callout list">
<tr>
<td width="12" valign="top" align="left"><a href="#re.phone.4.1"><img src="../images/callouts/1.png" alt="1" border="0" width="12" height="12"></a>
</td>
<td valign="top" align="left">The only change you've made since that last step is changing all the <tt class="literal">+</tt> to <tt class="literal">*</tt>. Instead of <tt class="literal">\D+</tt> between the parts of the phone number, you now match on <tt class="literal">\D*</tt>. Remember that <tt class="literal">+</tt> means “<span class="quote">1 or more</span>”? Well, <tt class="literal">*</tt> means “<span class="quote">zero or more</span>”. So now you should be able to parse phone numbers even when there is no separator character at all.
</td>
</tr>
<tr>
<td width="12" valign="top" align="left"><a href="#re.phone.4.2"><img src="../images/callouts/2.png" alt="2" border="0" width="12" height="12"></a>
</td>
<td valign="top" align="left">Lo and behold, it actually works. Why? You matched the beginning of the string, then a remembered group of three digits
(<tt class="literal">800</tt>), then zero non-numeric characters, then a remembered group of three digits (<tt class="literal">555</tt>), then zero non-numeric characters, then a remembered group of four digits (<tt class="literal">1212</tt>), then zero non-numeric characters, then a remembered group of an arbitrary number of digits (<tt class="literal">1234</tt>), then the end of the string.
</td>
</tr>
<tr>
<td width="12" valign="top" align="left"><a href="#re.phone.4.3"><img src="../images/callouts/3.png" alt="3" border="0" width="12" height="12"></a>
</td>
<td valign="top" align="left">Other variations work now too: dots instead of hyphens, and both a space and an <tt class="literal">x</tt> before the extension.
</td>
</tr>
<tr>
<td width="12" valign="top" align="left"><a href="#re.phone.4.4"><img src="../images/callouts/4.png" alt="4" border="0" width="12" height="12"></a>
</td>
<td valign="top" align="left">Finally, you've solved the other long-standing problem: extensions are optional again. If no extension is found, the <tt class="function">groups()</tt> method still returns a tuple of four elements, but the fourth element is just an empty string.
</td>
</tr>
<tr>
<td width="12" valign="top" align="left"><a href="#re.phone.4.5"><img src="../images/callouts/5.png" alt="5" border="0" width="12" height="12"></a>
</td>
<td valign="top" align="left">I hate to be the bearer of bad news, but you're not finished yet. What's the problem here? There's an extra character before
the area code, but the regular expression assumes that the area code is the first thing at the beginning of the string. No
problem, you can use the same technique of “<span class="quote">zero or more non-numeric characters</span>” to skip over the leading characters before the area code.
</td>
</tr>
</table>
</div>
</div>
<p>The next example shows how to handle leading characters in phone numbers.</p>
<div class="example"><a name="d0e19318"></a><h3 class="title">Example 7.14. Handling Leading Characters</h3><pre class="screen">
<tt class="prompt">>>> </tt><span class="userinput">phonePattern = re.compile(r<span class='pystring'>'^\D*(\d{3})\D*(\d{3})\D*(\d{4})\D*(\d*)$'</span>)</span> <a name="re.phone.5.1"></a><img src="../images/callouts/1.png" alt="1" border="0" width="12" height="12">
<tt class="prompt">>>> </tt><span class="userinput">phonePattern.search(<span class='pystring'>'(800)5551212 ext. 1234'</span>).groups()</span> <a name="re.phone.5.2"></a><img src="../images/callouts/2.png" alt="2" border="0" width="12" height="12">
<span class="computeroutput">('800', '555', '1212', '1234')</span>
<tt class="prompt">>>> </tt><span class="userinput">phonePattern.search(<span class='pystring'>'800-555-1212'</span>).groups()</span> <a name="re.phone.5.3"></a><img src="../images/callouts/3.png" alt="3" border="0" width="12" height="12">
<span class="computeroutput">('800', '555', '1212', '')</span>
<tt class="prompt">>>> </tt><span class="userinput">phonePattern.search(<span class='pystring'>'work 1-(800) 555.1212 #1234'</span>)</span> <a name="re.phone.5.4"></a><img src="../images/callouts/4.png" alt="4" border="0" width="12" height="12">
<tt class="prompt">>>> </tt>
</pre><div class="calloutlist">
<table border="0" summary="Callout list">
<tr>
<td width="12" valign="top" align="left"><a href="#re.phone.5.1"><img src="../images/callouts/1.png" alt="1" border="0" width="12" height="12"></a>
</td>
<td valign="top" align="left">This is the same as in the previous example, except now you're matching <tt class="literal">\D*</tt>, zero or more non-numeric characters, before the first remembered group (the area code). Notice that you're not remembering
these non-numeric characters (they're not in parentheses). If you find them, you'll just skip over them and then start remembering
the area code whenever you get to it.
</td>
</tr>
<tr>
<td width="12" valign="top" align="left"><a href="#re.phone.5.2"><img src="../images/callouts/2.png" alt="2" border="0" width="12" height="12"></a>
</td>
<td valign="top" align="left">You can successfully parse the phone number, even with the leading left parenthesis before the area code. (The right parenthesis
after the area code is already handled; it's treated as a non-numeric separator and matched by the <tt class="literal">\D*</tt> after the first remembered group.)
</td>
</tr>
<tr>
<td width="12" valign="top" align="left"><a href="#re.phone.5.3"><img src="../images/callouts/3.png" alt="3" border="0" width="12" height="12"></a>
</td>
<td valign="top" align="left">Just a sanity check to make sure you haven't broken anything that used to work. Since the leading characters are entirely
optional, this matches the beginning of the string, then zero non-numeric characters, then a remembered group of three digits
(<tt class="literal">800</tt>), then one non-numeric character (the hyphen), then a remembered group of three digits (<tt class="literal">555</tt>), then one non-numeric character (the hyphen), then a remembered group of four digits (<tt class="literal">1212</tt>), then zero non-numeric characters, then a remembered group of zero digits, then the end of the string.
</td>
</tr>
<tr>
<td width="12" valign="top" align="left"><a href="#re.phone.5.4"><img src="../images/callouts/4.png" alt="4" border="0" width="12" height="12"></a>
</td>
<td valign="top" align="left">This is where regular expressions make me want to gouge my eyes out with a blunt object. Why doesn't this phone number match?
Because there's a <tt class="literal">1</tt> before the area code, but you assumed that all the leading characters before the area code were non-numeric characters (<tt class="literal">\D*</tt>). Aargh.
</td>
</tr>
</table>
</div>
</div>
<p>Let's back up for a second. So far the regular expressions have all matched from the beginning of the string. But now you
see that there may be an indeterminate amount of stuff at the beginning of the string that you want to ignore. Rather than
trying to match it all just so you can skip over it, let's take a different approach: don't explicitly match the beginning
of the string at all. This approach is shown in the next example.
</p>
<div class="example"><a name="d0e19396"></a><h3 class="title">Example 7.15. Phone Number, Wherever I May Find Ye</h3><pre class="screen">
<tt class="prompt">>>> </tt><span class="userinput">phonePattern = re.compile(r<span class='pystring'>'(\d{3})\D*(\d{3})\D*(\d{4})\D*(\d*)$'</span>)</span> <a name="re.phone.6.1"></a><img src="../images/callouts/1.png" alt="1" border="0" width="12" height="12">
<tt class="prompt">>>> </tt><span class="userinput">phonePattern.search(<span class='pystring'>'work 1-(800) 555.1212 #1234'</span>).groups()</span> <a name="re.phone.6.2"></a><img src="../images/callouts/2.png" alt="2" border="0" width="12" height="12">
<span class="computeroutput">('800', '555', '1212', '1234')</span>
<tt class="prompt">>>> </tt><span class="userinput">phonePattern.search(<span class='pystring'>'800-555-1212'</span>)</span> <a name="re.phone.6.3"></a><img src="../images/callouts/3.png" alt="3" border="0" width="12" height="12">
<span class="computeroutput">('800', '555', '1212', '')</span>
<tt class="prompt">>>> </tt><span class="userinput">phonePattern.search(<span class='pystring'>'80055512121234'</span>)</span> <a name="re.phone.6.4"></a><img src="../images/callouts/4.png" alt="4" border="0" width="12" height="12">
<span class="computeroutput">('800', '555', '1212', '1234')</span>
</pre><div class="calloutlist">
<table border="0" summary="Callout list">
<tr>
<td width="12" valign="top" align="left"><a href="#re.phone.6.1"><img src="../images/callouts/1.png" alt="1" border="0" width="12" height="12"></a>
</td>
<td valign="top" align="left">Note the lack of <tt class="literal">^</tt> in this regular expression. You are not matching the beginning of the string anymore. There's nothing that says you need
to match the entire input with your regular expression. The regular expression engine will do the hard work of figuring out
where the input string starts to match, and go from there.
</td>
</tr>
<tr>
<td width="12" valign="top" align="left"><a href="#re.phone.6.2"><img src="../images/callouts/2.png" alt="2" border="0" width="12" height="12"></a>
</td>
<td valign="top" align="left">Now you can successfully parse a phone number that includes leading characters and a leading digit, plus any number of any
kind of separators around each part of the phone number.
</td>
</tr>
<tr>
<td width="12" valign="top" align="left"><a href="#re.phone.6.3"><img src="../images/callouts/3.png" alt="3" border="0" width="12" height="12"></a>
</td>
<td valign="top" align="left">Sanity check. this still works.</td>
</tr>
<tr>
<td width="12" valign="top" align="left"><a href="#re.phone.6.4"><img src="../images/callouts/4.png" alt="4" border="0" width="12" height="12"></a>
</td>
<td valign="top" align="left">That still works too.</td>
</tr>
</table>
</div>
</div>
<p>See how quickly a regular expression can get out of control? Take a quick glance at any of the previous iterations. Can
you tell the difference between one and the next?
</p>
<p>While you still understand the final answer (and it is the final answer; if you've discovered a case it doesn't handle, I
don't want to know about it), let's write it out as a verbose regular expression, before you forget why you made the choices
you made.
</p>
<div class="example"><a name="d0e19458"></a><h3 class="title">Example 7.16. Parsing Phone Numbers (Final Version)</h3><pre class="screen">
<tt class="prompt">>>> </tt><span class="userinput">phonePattern = re.compile(r<span class='pystring'>'''
# don't match beginning of string, number can start anywhere
(\d{3}) # area code is 3 digits (e.g. '800')
\D* # optional separator is any number of non-digits
(\d{3}) # trunk is 3 digits (e.g. '555')
\D* # optional separator
(\d{4}) # rest of number is 4 digits (e.g. '1212')
\D* # optional separator
(\d*) # extension is optional and can be any number of digits
$ # end of string
'''</span>, re.VERBOSE)</span>
<tt class="prompt">>>> </tt><span class="userinput">phonePattern.search(<span class='pystring'>'work 1-(800) 555.1212 #1234'</span>).groups()</span> <a name="re.phone.7.1"></a><img src="../images/callouts/1.png" alt="1" border="0" width="12" height="12">
<span class="computeroutput">('800', '555', '1212', '1234')</span>
<tt class="prompt">>>> </tt><span class="userinput">phonePattern.search(<span class='pystring'>'800-555-1212'</span>)</span> <a name="re.phone.7.2"></a><img src="../images/callouts/2.png" alt="2" border="0" width="12" height="12">
<span class="computeroutput">('800', '555', '1212', '')</span>
</pre><div class="calloutlist">
<table border="0" summary="Callout list">
<tr>
<td width="12" valign="top" align="left"><a href="#re.phone.7.1"><img src="../images/callouts/1.png" alt="1" border="0" width="12" height="12"></a>
</td>
<td valign="top" align="left">Other than being spread out over multiple lines, this is exactly the same regular expression as the last step, so it's no
surprise that it parses the same inputs.
</td>
</tr>
<tr>
<td width="12" valign="top" align="left"><a href="#re.phone.7.2"><img src="../images/callouts/2.png" alt="2" border="0" width="12" height="12"></a>
</td>
<td valign="top" align="left">Final sanity check. Yes, this still works. You're done.</td>
</tr>
</table>
</div>
</div>
<div class="furtherreading">
<h3>Further Reading on Regular Expressions</h3>
<ul>
<li><a href="http://py-howto.sourceforge.net/regex/regex.html">Regular Expression HOWTO</a> teaches about regular expressions and how to use them in <span class="application">Python</span>.
</li>
<li><a href="http://www.python.org/doc/current/lib/"><i class="citetitle"><span class="application">Python</span> Library Reference</i></a> summarizes the <a href="http://www.python.org/doc/current/lib/module-re.html"><tt class="filename">re</tt> module</a>.
</li>
</ul>
</div>
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