XPath
🔗 Original page — Source of this material
This is a flexible and powerful query language for selecting elements in XML or (X)HTML documents and for XSLT transformations by DOM. It is a standard created by the W3C consortium.
What is XPath for in ZennoPoster?
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For parsing data from websites (action ❗→ Parse data)
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For searching for and interacting with web page elements
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You can use it in the ❗→ Action Builder.
With XPath, you can create a more universal and robust data search algorithm that is less sensitive to website layout changes compared to ❗→ regular expressions. This query language allows you to significantly simplify parser logic and speed up development.
Testing queries as you create them
- ZennoPoster comes with a built-in ❗→ X/Json Path Tester that lets you test the expressions you've created.
- You can also build and test XPath expressions in the ❗→ Web Developer Tools (DevTools) window: open DevTools, press ctrl+f to open the search bar, and enter your XPath expression there:
For example, to get the names of events on the http://w3.org website, you can use the following expression:
//*[@id="w3c_home_upcoming_events"]/ul/li//a
Basic syntax
Paths
| Expression | Description |
|---|---|
| . | current context |
| .// | recursive descent (zero or more levels down from the current context) |
| /html/body | absolute path |
| a | relative path |
| //* | everything in the current context |
| li//a | links that are “grandchildren” of li |
| //a|//button | links and buttons (combines two node sets) |
Relationships
| Expression | Description |
|---|---|
| a/i/parent::p | immediate parent <p> |
| p/ancestor::\ | all ancestors |
| p/following-sibling::\ | all following siblings |
| p/preceding-sibling::\ | all preceding siblings |
| p/following::\ | all elements after except descendants |
| p/preceding::\ | all elements before except ancestors |
| p/descendant-or-self::\ | the context node and all its descendants |
| p/ancestor-or-self::\ | the context node and all its ancestors |
Getting nodes
| Expression | Description |
|---|---|
| /div/text() | get text nodes |
| /div/text()[1] | get the first text node |
Element position
| Expression | Description |
|---|---|
| a[1] | first element |
| a[last()] | last element |
| a[2] | second link |
| a[position() <= 3] | first 3 links |
| ul[li[1]=”OK”] | list (UL) whose first item is 'OK' |
| tr[position() mod 2 = 1] | odd elements |
| tr[position() mod 2 = 0] | even elements |
| p/text()[2] | second text node |
Attributes and filters [] - means filtering elements
| Expression | Description |
|---|---|
| input[@type=”text”] | <input> tag with type attribute equal to text |
| input[@class='OK'] | <input> tag with class attribute equal to OK |
| p[not(@)] | paragraphs with no attributes |
| [@style] | all elements with a style attribute |
| a[. = “OK”] | links with value “OK” |
| a/@id | link IDs |
| a/@\ | all link attributes |
| links that have both id and rel attributes |
| a[i or b] | links containing an <i> or <b> element |
Functions
Basic Xpath functions - http://www.w3.org/TR/xpath/#corelib
| Function | Description | Example |
|---|---|---|
| name() | Returns the element name | [name()='a'] |
| string(val) | Get the value of an attribute | string(a[1]/@id) |
| substring(val, from, to) | Cut part of a string | substring(@id, 1, 6) |
| substring-before(val, to) | Return the part of val before the string to | substring-before('12-May-1998', '-') = '12' |
| substring-after(val, from) | Return the part of val after the string to | substring-after('12-May-1998', '-') = 'May-1998' |
| string-length() | Returns the number of characters in a string | [string-length(text()) > 5] |
| count() | Returns the number of elements | |
| concat() | Takes two or more strings and returns the concatenation of its arguments. | |
| normalize-space() | Just like Trim | [normalize-space(text())='SEARCH'] |
| starts-with() | Starts with | [starts-with(text(), 'SEARCH')] |
| contains() | Contains | [contains(name(), 'SEARCH')] |
| translate(val, from, to) | Replaces the characters in the first string argument that appear in the second argument with the corresponding characters in the third argument. | translate(«bar»,«abc»,«ABC») |
Grouping
| Expression | Description |
|---|---|
| (table/tbody/tr)[last()] | the last <tr> row of all tables |
| (//h1|//h2)[contains(text(), 'Text')] | heading 1 or 2 containing 'Text' |
| a[//tr/@data-id=@data-id] | all links whose data-id attribute matches the data-id attribute of a table row |
Useful links
https://ru.wikipedia.org/wiki/XPath https://www.w3schools.com/xml/xpath_syntax.asp