34 lines
2 KiB
Markdown
34 lines
2 KiB
Markdown
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---
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obj: concept
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wiki: https://en.wikipedia.org/wiki/XPath
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---
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# XPath
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XPath ([XML](XML.md) Path Language) is a powerful query language used to navigate and select elements from [XML](XML.md) documents. It is commonly employed in web scraping, [XML](XML.md) processing, and testing scenarios.
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## XPath Syntax
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XPath expressions use a path notation to identify and navigate [XML](XML.md) elements. The basic syntax includes:
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- **Node Selection:** `/` is used to select the root node. `element` selects all child elements of the current node with the specified name: `/root/element`
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- **Wildcards:** The `*` symbol is used as a wildcard for any element. `/root/*`
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- **Predicates:** Square brackets `[]` are used to specify conditions for node selection. `/root/element[@attribute='value']`
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### Absolute XPath
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Absolute XPath provides the complete path from the root node to the desired element. It starts with a single forward slash `/`.
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`/html/body/div[1]/p[2]`
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### Relative XPath
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Relative XPath selects elements based on their relationship to other elements. It does not start from the root, allowing for more flexible and adaptable expressions.
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`//div[@class='example']/a`
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### XPath Functions
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XPath provides various functions for more complex queries. Examples include `text()`, `contains()`, and `position()`.
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`//h2[contains(text(),'XPath')]`
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Some functions include:
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- `text()`: The `text()` function is used to select the text content of an element.
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- `contains(element, value)`: The `contains()` function is used to check if a string contains a specific substring.
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- `starts-with(element, value)`: The `starts-with()` function is used to check if a string starts with a specified prefix.
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- `concat(elements...)`: The `concat()` function concatenates two or more strings.
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- `not(element)`: The `not()` function negates a given expression.
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- `position()`: The `position()` function returns the position of the current node in the selection.
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- `last()`: The `last()` function returns the position of the last node in the selection.
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