# Selene API
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[[src]](https://github.com/yashaka/selene)
The core of the Selene library. Main methods are ```open_url```, ```s``` and ```ss```:
## ```open_url```
To visit page you can just specify url:
```browser.open_url('http://chromedriver.storage.googleapis.com/index.html?path=2.9')```
But it is better to specify base url and use relative urls to visit pages:
```config.app_host = 'http://chromedriver.storage.googleapis.com'```
```browser.open_url('/index.browser.open_urlhtml?path=2.9')```
## ```s``` and ```ss```
```s(cssSelector)``` – returns object of the SeleneElement class that represents first element found by CSS selector on the page.
```s(by.*)``` – returns "first SeleneElement" by the locator of the By class
```ss(cssSelector)``` – returns object of type ElementsCollection that represents collection of all elements found by a CSS selector.
```ss(by.*)``` – returns "collection of elements" by the locator of By type
You can also use alias methods for your taste:
```
tasks[2].s(".toggle").click()
```
instead of
```
tasks[2].element(".toggle").click()
```
After you receive a SeleneElement object be the "s" command, you can perform some actions or actions with it:
```
s('#toggle-all').click()
```
```
s('#new-todo').set_value(task_text).press_enter()
```
or check some condition:
```
s('#todo-count').should(have.text('3'))
```
If we are looking for a specific element from a group of the same type, it is convenient to use the command ```"ss"```
For example, instead of a long expression
```
s("//*[@id='todo-list']/li[.//text()='b']//*[@class='toggle']").click()
```
you can use a much more readable chain of methods
```
ss('#todo-list>li').element(by.exact_text('b')).find('.toggle').click()
```
Another plus of such chains of methods is that we get a more informative error message. It makes it possible to identify which of the "links" of the chain did not work. In the first version, we get only a message that the method did not work.
In case you need to reuse some parts elsewhere - go ahead and move your locators:
```
tasks = ss("#todo-list>li")
active = have.css_class("active")
completed = have.css_class("completed")
```