# Selector

### What is selector?

The purpose of designing a selector is to distinguish various methods of selecting HTML elements (xpath, css, regex). We will use a selector to select the list elements in the HTML. Of course, we also need to use selectors to select the WebElement of [selenium](https://www.selenium.dev/), so that the framework can operate on click events. If you don't know what selenium is, please learn it first.

{% embed url="<https://www.selenium.dev/>" %}

### type of selector

```python
import crawlist as cl
# These selectors are designed to select list elements from web page text
css_selector = cl.CssSelector('your css')
xpath_selector = cl.XpathSelector('your xpath')
regex_selector = cl.RegexSelector('your regex')

# These selectors are designed to select the buttons in the webpage that involve data increment
css_webe_selector = cl.CssWebElementSelector('the button css')
xpath_webe_selector = cl.XpathWebElementSelector('the button xpath')
```

### How to implement your own selector

I think the above selectors are sufficient for use, but if you still want to implement your own selector, you can follow the following code to do it.

```python
import crawlist as cl

class MySelector(cl.Selector):
    
    # You need to rewrite the select() and valid() methods.
    # The select method needs to select the list you need from the HTML text.
    def select(self, html: str) -> list[str]:
        pattern = self.pattern
        raise NotImplementedError
    # The purpose of the valid method is to verify your pattern, and you can also ignore it.
    def valid(self, pattern) -> bool:
        raise NotImplementedError
```


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