With XPath, you can extract data based on text elements' contents, and not only on the page structure. So when you are scraping the web and you run into a hard-to-scrape website, XPath may just save the day and a bunch of your time!
This is an introductory tutorial that will walk you through the basic concepts of XPath, crucial to a good understanding of it, before diving into more complex use cases. Just paste the HTML samples provided in this post and play with the expressions. This tree's root node is not part of the document itself.
Distinguishing between these different types is useful to understand how XPath expressions work. Now let's start digging into XPath. This is what we call a location path. It allows us to specify the path from the context node in this case the root of the tree to the element we want to select, as we do when addressing files in a file system.
The location path above has three location steps , separated by slashes. The context node changes in each step. For example, the head node is the context node when the last step is being evaluated. We can select them using:. In fact, the expressions we've just seen are using XPath's abbreviated syntax. This part of the expression is called the axis and it specifies a set of nodes to select from, based on their direction on the tree from the current context downwards, upwards, on the same tree level.
The next part of the expression, node , is called a node test , and it contains an expression that is evaluated to decide whether a given node should be selected or not. In this case, it selects nodes from all types. Then we have another axis, child which means go to the child nodes from the current context , followed by another node test, which selects the nodes named as title. So, the axis defines where in the tree the node test should be applied and the nodes that match the node test will be returned as a result.
This expression selects the text nodes from inside p elements. Consider this HTML document:. Say we want to select only the first li node from the snippet above. We can do this with:. In this case, it checks each node's position using the position function, which returns the position of the current node in the resulting node-set notice that positions in XPath start at 1, not 0. We can abbreviate the expression above to:. In fact, much of the notation of directory paths is carried over intact:.
To select a specific h2 element, you use square brackets [] for indexing like those used for arrays. That is a fairly common convention for XML documents. However, uppercase names are easier to read in a tutorial like this one. Attribute names, on the other hand, will remain in lowercase. A name specified in an XPath expression refers to an element.
To refer to an attribute, you prefix the attribute name with an sign. For example, type refers to the type attribute of an element. The full range of XPath expressions takes advantage of the wild cards, operators, and functions that XPath defines.
You will learn more about those shortly. Here, we look at a couple of the most common XPath expressions simply to introduce them. You can combine those two notations to get something interesting. In XPath, the square-bracket notation [] normally associated with indexing is extended to specify selection criteria. Similar expressions exist for elements. Each element has an associated string-value, which is formed by concatenating all the text segments that lie under the element.
A more detailed explanation of how that process works is presented in String-Value of an Element. Here are other examples that use the extended square-bracket notation:. The XPath specification defines quite a few addressing mechanisms, and they can be combined in many different ways. As a result, XPath delivers a lot of expressive power for a relatively simple specification. This section illustrates other interesting combinations:. Note - Many more combinations of address operators are listed in section 2.
This is arguably the most useful section of the specification for defining an XSLT transform. By definition, an unqualified XPath expression selects a set of XML nodes that matches that specified pattern. Table lists the wild cards that can be used in XPath expressions to broaden the scope of the pattern matching. It is also applicable if any one condition is true or maybe both. Means any one condition should be true to find the element.
In the below XPath expression, it identifies the elements whose single or both conditions are true. In AND expression, two conditions are used, both conditions should be true to find the element. It fails to find element if any one condition is false. XPath starts-with is a function used for finding the web element whose attribute value gets changed on refresh or by other dynamic operations on the webpage.
In this method, the starting text of the attribute is matched to find the element whose attribute value changes dynamically. You can also find elements whose attribute value is static not changes. The XPath text function is a built-in function of selenium webdriver which is used to locate elements based on text of a web element. It helps to find the exact text elements and it locates the elements within the set of text nodes.
The elements to be located should be in string form. In this expression, with text function, we find the element with exact text match as shown below. These XPath axes methods are used to find the complex or dynamic elements. Below we will see some of these methods. Selects all elements in the document of the current node [ UserID input box is the current node] as shown in the below screen. If you want to focus on any particular element then you can use the below XPath method:.
The ancestor axis selects all ancestors element grandparent, parent, etc. If you want to focus on any particular element then you can use the below XPath, where you change the number 1, 2 as per your requirement:.
If you want to focus on any particular element then you can use the below xpath:. If you want to focus on any particular element then you can use the below XPath:.
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