XPath expression to add to code that already finds cities, that might also retrieve nearby zip codes

Question

After much manual effort, I have created XPath expressions that retrieve from parsed website HTML the cities in which nearly 100 companies have offices. To late it dawned on me that zip codes for those cities would be excellent and distinctive.

I realize that no single piece of additional XPath code will cover all situations, but is there some generic expression that might reasonably often retrieve 5 digits in a row (or 5 digits, a hyphen and 4 digits) in the same or nearby namespace [assume zip codes come after city]?

For example, the code

//div[@class='content']//h5

might add something like "and \\d{5}" [I am not adept with XPath and am using R regex syntax with backslashes for five and only five digits]. I could then quickly paste on the additional code and see whether it brings back zip codes, doing the rest by hand.

RESPONDING TO COMMENTS:

Here is one of hundreds of HTML codes:

<div class="container">
<script type="text/javascript">
<div class="header">
<table>
<tbody>
<tr>
<td class="bodywrap" valign="top">
<table width="100%" cellspacing="0" cellpadding="0" border="0">
<table class="body" width="100%" cellspacing="0" cellpadding="20" border="0">
<tbody>
<tr>
<td>
<table class="body" width="100%" cellspacing="3" cellpadding="0" border="0">
<tbody>
<tr valign="top">
<td width="50%">
<table width="100%" cellspacing="0" cellpadding="0">
<img border="0" src="/files/Office/ac28ef17-906a-4ed0-9850-0af853da6abe/Presentation/ceOfficeNameImage/t_NewYork.gif">
<br>
<br>
1251 Avenue of the Americas
<br>
New York, New York 10020
<br>
T:
<span class="skype_c2c_print_container notranslate">212.262.6700</span>

I have tried this XPath expresssion, which does not succeed. Even if it were to extract "New York" I would like to be able to extract "10020".

I am on Windows 8 with XML 1.0 (there is no XML 2.0 according to a 2013 SO post).

RESPONDING TO COMMENT: Here is an example of code I use.

doc <- htmlTreeParse("http://www.butlersnow.com/Contact_Us.aspx", useInternal = TRUE)
xpathSApply(doc, "//div[@class='content']//h5", xmlValue, trim = TRUE)

Answer 1

So, we've already found out that you

• Are using packages in R that offer HTML parsing and XPath functionality
• Are looking for an XPath expression that singles out a particular sequence of characters from HTML text content

What we have not yet established is which version of XPath is supported by this module in the R language. Either it only conforms to the XPath 1.0 standard (more likely) or it also supports XPath 2.0.

Why is this relevant? It's relevant because only XPath 2.0 offers functions that can handle regular expressions. Regexes are there to solve the very problem you describe, that is, finding 5 digits in a row in arbitrary strings. Now, how do you find out which version is supported? Simply use a function that is only available in XPath 2.0, for example tokenize() and see if this raises an error.

Option 1: This R functionality turns out to support XPath 2.0

First, identify the elements that are likely to contain the ZIP code. As an example let's say it is inside an h5element. Then, use the matches() function together with a regular expression.

//h5[matches(.,'\d{5}')]

Or a slight variation of this. Of course, R cannot discriminate between actual ZIP codes and other things that simply consist of five digits in a row by chance.

Option 2: Only XPath 1.0 is at your disposal

Then, in my opinion, there is no reasonable way to combine this into a single XPath expression because regexes are not available. But, R itself happens to be good at regular expressions. Extract all relevant strings from HTML with XPath and then search them with regexes in R, outside XPath.

---

Note: All this does not in any way "prove" that a regular expression as simple as this is precise and restrictive enough to find ZIP codes only. In a large collection of HTML documents, there might be a lot of "false positives" that cannot be distinguished from "real" hits. Then, you'd have to refine the method, e.g. check the results against a database of ZIP codes.

Since I am writing anyway, there is no such thing as a "nearby namespace". You are mistaking what in XPath is called the context item for a namespace. In the following example, http://www.ns.com is a namespace.

<ns:root xmlns:ns="http://www.ns.com">
  <ns:a/>
</ns:root>