> For the complete documentation index, see [llms.txt](https://developers.oxylabs.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://developers.oxylabs.io/products/cn/web-scraper-api/features/custom-parser/writing-instructions-manually/list-of-functions/function-examples.md).
# 解析函数示例
自定义解析器函数的实用示例，涵盖 HTML 处理、字符串操作、数学运算和常见解析任务。
## HTML 处理
### `element_text`
#### 示例 HTML
```html
```
**从 HTML 元素中提取文本并去除空白**
```json
{
"price": {
"_fns": [
{
"_fn": "xpath_one",
"_args": [".//*[@id='product-price']"]
},
{
"_fn": "element_text"
}
]
}
}
```
```json
{
"price": "12 3"
}
```
**将字符串值作为输入时，不执行任何操作**
```json
{
"price": {
"_fns": [
{
"_fn": "xpath_one",
"_args": [".//*[@id='product-price']/text()"]
},
{
"_fn": "element_text"
}
]
}
}
```
```json
{
"price": " 12 3\n\n\n "
}
```
### `xpath`
#### 示例 HTML
```html
```
**获取所有描述项**
```json
{
"description_items": {
"_fns": [
{
"_fn": "xpath",
"_args": ["//li[@class='description-item']/text()"]
}
]
}
}
```
```json
{
"description_items": ["非常", "不错", "袜子"]
}
```
**获取第一个描述项**
```json
{
"first_description_item": {
"_fns": [
{
"_fn": "xpath",
"_args": ["(//li[@class='description-item'])[1]/text()"]
}
]
}
}
```
```json
{
"first_description_item": [
"非常"
]
}
```
**检查描述区块元素是否存在**
```json
{
"description_section_exists": {
"_fns": [
{
"_fn": "xpath",
"_args": ["boolean(//div[@class='description'])"]
}
]
}
}
```
```json
{
"description_section_exists": true
}
```
**将价格作为数字获取**
```json
{
"price": {
"_fns": [
{
"_fn": "xpath",
"_args": ["number(//div[@class='price'])"]
}
]
}
}
```
```json
{
"description_section_exists": 123.12
}
```
**当当前表达式失败时回退到多个表达式**
```json
{
"price": {
"_fns": [
{
"_fn": "xpath",
"_args": [
"//div[@class='product-price']/text()", <--- 这不会找到任何内容
"//div[@class='price']/text()" <--- 这会找到目标价格
]
}
]
}
}
```
```json
{
"price": [
"123.12"
]
}
```
**XPath `|` 用于匹配多个表达式的运算符**
```json
{
"price_and_title": {
"_fns": [
{
"_fn": "xpath",
"_args": ["//div[@class='price']/text() | //div[@class='title']/text()"]
}
]
}
}
```
```json
{
"price_and_title": [
"袜子",
"123.12"
]
}
```
### `xpath_one`
#### 示例 HTML
```html
```
**返回第一个匹配项**
```json
{
"first_description_item": {
"_fns": [
{
"_fn": "xpath_one",
"_args": [".//li/text()"]
}
]
}
}
```
```json
{
"first_description_item": "非常"
}
```
**使用 XSLT 函数**
```json
{
"price": {
"_fns": [
{
"_fn": "xpath_one",
"_args": ["number(.//div[@class='price'])"]
}
]
}
}
```
```json
{
"price": 123.12
}
```
## 字符串处理
### `amount_from_string`
#### 示例 HTML
```html
```
**从字符串中提取金额**
```json
{
"price": {
"_fns": [
{
"_fn": "xpath_one",
"_args": [".//div[@class='price']/text()"]
},
{
"_fn": "amount_from_string"
}
]
}
}
```
```json
{
"price": 123.12
}
```
### `amount_range_from_string`
#### 示例 HTML
```html
价格是：123.12 比索；
价格是：345.12 比索；
价格是：678.12 比索
```
**从字符串中提取所有金额**
```json
{
"prices": {
"_fns": [
{
"_fn": "xpath_one",
"_args": [".//div[@class='price']/text()"]
},
{
"_fn": "amount_range_from_string"
}
]
}
}
```
```json
{
"prices": [
123.12,
345.12,
678.12
]
}
```
### `连接`
#### 示例 HTML
```html
价格是：123.12 比索；
价格是：345.12 比索；
价格是：678.12 比索
```
**将字符串数组连接为一个字符串**
```json
{
"price_variants": {
"_fns": [
{
"_fn": "xpath",
"_args": [".//div[@class='price']"]
},
{ // 如果我们在第一个流水线函数中调用 normalize-space(),
// 它将只返回第一个值。
"_fn": "xpath",
"_args": ["normalize-space(text())"]
},
{
"_fn": "join",
"_args": ""
}
]
}
}
```
```json
{
"price_variants": "价格是：123.12 比索；价格是：345.12 比索；价格是：678.12 比索"
}
```
### `regex_find_all`
#### 示例 HTML
```html
```
**查找两个字符之间的所有匹配**
```json
{
"descriptions": {
"_fns": [
{
"_fn": "xpath_one",
"_args": [".//div[@class='description']/text()"]
},
{
"_fn": "regex_find_all",
"_args": ["\\[(.*)\\]"]
}
]
}
}
```
```json
{
"descriptions": [
"一个描述",
"两个描述",
"三个描述"
]
}
```
### `regex_search`
#### 示例 HTML
```html
[一个描述]
[两个描述]
[三个描述]
{我需要的那个}
```
**返回两个字符之间的描述**
```json
{
"description": {
"_fns": [
{
"_fn": "xpath_one",
"_args": [".//div[@class='description']/text()"]
},
{
"_fn": "regex_search",
"_args": ["{(.*)}", 1]
}
]
}
}
```
```json
{
"description": "我需要的那个"
}
```
### `regex_substring`
#### 示例 HTML
```html
* 一个描述
* 两个描述
* 三个描述
* {我想替换掉这个}
```
**用指定值替换文本的一部分**
```json
{
"descriptions": {
"_fns": [
{
"_fn": "xpath_one",
"_args": [".//div[@class='description']/text()"]
},
{
"_fn": "regex_substring",
"_args": ["{我想替换掉这个}", "four description"]
},
{
"_fn": "regex_find_all",
"_args": ["\\*\\s(.*)\n"]
}
]
}
}
```
```json
{
"descriptions": [
"一个描述",
"两个描述",
"three description",
"four description"
]
}
```
## 常用函数
### `convert_to_*`
#### 示例 HTML
```html
```
**获取价格变体的数量**
```json
{
"price_variants": {
"_fns": [
{
"_fn": "xpath",
"_args": [".//div[@class='price']"]
},
{
"_fn": "length"
}
]
}
}
```
```json
{
"price_variants": 5
}
```
**获取多维数组中价格变体的数量**
示例 HTML：
```html
```
```json
{
"number_of_variants": {
"_fns": [
{
"_fn": "xpath",
"_args": [".//property"]
},
{
"_fn": "xpath",
"_args": [".//option"]
},
{
"_fn": "length"
}
]
}
}
```
```json
{
"number_of_variants": [
3,
3
]
}
```
### `select_nth`
#### 示例 HTML
```html
```
**从数组中选择第一个描述项**
```json
{
"price_and_title": {
"_fns": [
{
"_fn": "xpath",
"_args": ["//li[@class='description-item']/text()"]
},
{
"_fn": "select_nth",
"_args": 0
}
]
}
}
```
```json
{
"price_and_title": "非常"
}
```
**从数组中选择最后一个描述项**
```json
{
"description_item": {
"_fns": [
{
"_fn": "xpath",
"_args": ["//li[@class='description-item']/text()"]
},
{
"_fn": "select_nth",
"_args": -1
}
]
}
}
```
```json
{
"description_item": "袜子"
}
```
## 数学函数
### `平均值`
#### 示例 HTML
```html
```
**计算所有列出价格的平均值**
```json
{
"price_average": {
"_fns": [
{
"_fn": "xpath",
"_args": [".//div[@class='price']"]
},
{
"_fn": "xpath_one",
"_args": ["number(text())"]
},
{
"_fn": "average"
}
]
}
}
```
```json
{
"price_average": 244.8
}
```
### `最大值`
#### 示例 HTML
```html
```
**计算所有列出价格的最大值**
```json
{
"price_max": {
"_fns": [
{
"_fn": "xpath",
"_args": [".//div[@class='price']"]
},
{
"_fn": "xpath_one",
"_args": ["number(text())"]
},
{
"_fn": "max"
}
]
}
}
```
```json
{
"price_max": 456.0
}
```
### `最小值`
#### 示例 HTML
```html
```
**计算所有列出价格的平均值**
```json
{
"price_min": {
"_fns": [
{
"_fn": "xpath",
"_args": [".//div[@class='price']"]
},
{
"_fn": "xpath_one",
"_args": ["number(text())"]
},
{
"_fn": "min"
}
]
}
}
```
```json
{
"price_min": 100.0
}
```
### `乘积`
#### 示例 HTML
```html
```
**获取不同产品变体的数量**
```json
{
"number_of_variants": {
"_fns": [
{
"_fn": "xpath",
"_args": [".//property"]
},
{
"_fn": "xpath",
"_args": [".//option"]
},
{
"_fn": "length"
},
{
"_fn": "product"
}
]
}
}
```
```json
{
"number_of_variants": 12
}
```
---
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