css selector 通常有以下几种方式确定元素：
下文所涉及的HTML代码：
<!DOCTYPE html>
<html>
<head>
<titile>Css selector 说明</title>
<style>
div{width: 100%;line-height:20px;
margin-top:10px;background-color:orange;}
/* [id]{background-color: red;} */
[id="two"]{background-color: blue;}
[class~="c2"]{font-size: 36px;color:white; background-color: yellow;}
[class|="five"]{font-size: 36px;color:white; background-color: gray;}
[id^="six"]{font-size: 36px;color:white; background-color: pink;}
[id$="ree"]{background-color:steelblue;}
</style>
</head>
<body>
<div id='one'>1</div>
<div id='two'>2</div>
<div id="three">3</div>
<div id="c1 c2 c3" id="four">4</div>
<div class="five-test">5</div>
<div id="six test">6</div>
<div>
<label class="hidden-label" for="Email">Test ID selector: </label>
<input id="Email" type="email" autofocus="" placeholder="Enter your email" name="Email" spellcheck="false" value="">
</div>
<div>
<label class="hidden-label" for="Email">Test Class selector: </label>
<input id="Passwd-hidden" class="password" type="password" spellcheck="false">
</div>
<div>
<label class="hidden-label" for="Test attribute">Test attribute: </label>
<input id="Test_attribute" class="inputtext" type="test email" tabindex="1" value="" name="test email">
</div>
<div>
<label class="hidden-label" for="Test SUB-STRING MATCHES">Test SUB-STRING MATCHES: </label>
<input id="Test_ID_001" >
</div>
<div id="buttonDiv" class="small">
<label class="hidden-label" for="Test SUB-STRING MATCHES">Test Child Elements: </label>
<input id="Child Elements" >
</div>
<div>
<label class="hidden-label" for="Test nth-child">Test nth-child: </label>
<ul id="automation">
<li>Selenium</li>
<li>Appium</li>
<li>Sikuli</li>
</ul>
</div>
<div>
<label class="hidden-label" for="Test inner-STRING">Test inner-STRING MATCHES: </label>
<button id="test-button" ><span>test1_button</span></button>
<button id="test2-button" ><span>test2_button</span></button>
</div>
<div><a herf="just a test">link</a></div>
</body>
</html>
测试Python代码（将上边代码保存为 test_css_selector.html）：
dr = webdriver.Chrome(r"your path/chromedriver.exe")
# 将上边代码保存为 test_css_selector.html
dr.get(r"file:///your path/test_css_selector.html")
dr.find_element_by_css_selector("input#Email").send_keys("test ID selector")
# dr.find_element_by_css_selector("#Email").send_keys("test ID selector")
# dr.find_element_by_css_selector("input.password").send_keys("test class selector")
dr.find_element_by_css_selector(".password").send_keys("test class selector")
ID 选择器
在CSS中，#表示选择ID属性，语法为：css=<HTML tag><#><ID属性值>或 css=<#><ID属性值>；例子：css="input#Email" 或 css="#Email"
HTML：
<div>
<label class="hidden-label" for="Email">Test ID selector: </label>
<input id="Email" type="email" autofocus="" placeholder="Enter your email" name="Email" spellcheck="false" value="">
</div>
代码：
# python 代码
dr.find_element_by_css_selector("input#Email").send_keys("test ID selector")
# dr.find_element_by_css_selector("#Email").send_keys("test ID selector")
# Java 代码
# driver.findElement(By.cssSelector("input#Email"));
# driver.findElement(By.cssSelector("#Email"));
Class 选择器
在CSS中，.表示选择class属性，语法为：css=<HTML tag><.><class属性值>或 css=<.><class属性值>；例子：css="input.password" 或 css=".password"
HTML：
<div>
<label class="hidden-label" for="Email">Test Class selector: </label>
<input id="Passwd-hidden" class="password" type="password" spellcheck="false">
</div>
代码：
# python 代码
dr.find_element_by_css_selector("input.password").send_keys("test class selector")
# dr.find_element_by_css_selector(".password").send_keys("test class selector")
# Java 代码
# driver.findElement(By.cssSelector("input.password"));
# driver.findElement(By.cssSelector(".password"));
Attribute 和Sub-String 选择器
属性选择器说明如下：
| 选择器类型 | 选择器说明 |
|---|---|
[attr] |
表示选择带有attr命名属性的所有元素 |
[attr=value] |
表示选择带有attr命名属性，且属性值为value的元素 |
[attr~=value] |
表示选择带有attr命名的属性，且该属性是一个一空格作为分隔符的值列表，至少有一个值为value |
[attr|=value] |
表示选择以attr命名属性，且属性值为value或者以value-为前缀开头 |
[attr^=value] |
表示带有以attr命名的属性，且属性值是以value开头的元素 |
[attr$=value] |
表示带有以attr命名的属性，且属性值是以value结尾的元素 |
[attr*=value] |
表示带有以attr命名的属性，且属性值包含有value的元素 |
默认代码：
<!DOCTYPE html>
<html>
<head>
<titile>Css selector 说明</title>
<style>
div{width: 100%;line-height:40px;
margin-top:20px;background-color:orange;}
</style>
</head>
<body>
<div id='one'>1</div>
<div id='two'>2</div>
<div id="three">3</div>
<div class="c1 c2 c3" id="four">4</div>
<div class="five-test">5</div>
<div id="six test">6</div>
</body>
</html>
效果图：
修改style代码如下：
<style>
div{width: 100%;line-height:40px;
margin-top:20px;background-color:orange;}
[id]{background-color: red;}
[id="two"]{background-color: blue;}
[class~="c2"]{font-size: 36px;color:white; background-color: yellow;}
[class|="five"]{font-size: 36px;color:white; background-color: gray;}
[id^="six"]{font-size: 36px;color:white; background-color: pink;}
[id$="ree"]{background-color:steelblue;}
</style>
修改后的效果图：
在CSS中，Attribute 选择器的语法可参考上边的说明，css=input[id='Test attribute']：
HTML：
<div id="c1 c2 c3" id="four">4</div>
<div class="five-test">5</div>
<div>
<label class="hidden-label" for="Test attribute">Test attribute: </label>
<input id="Test attribute" class="inputtext" type="test email" tabindex="1" value="" name="test email">
</div>
<div>
<label class="hidden-label" for="Test SUB-STRING MATCHES">Test SUB-STRING MATCHES: </label>
<input id="Test_ID_001" >
</div>
<div>
<label class="hidden-label" for="Test nth-child">Test nth-child: </label>
<ul id="automation">
<li>Selenium</li>
<li>Appium</li>
<li>Sikuli</li>
</ul>
</div>
代码：
dr.find_element_by_css_selector("input[type='test email']").send_keys("test attribute selector")
# dr.find_element_by_css_selector("input[id='Test_attribute'][type='test email']").send_keys("test attribute selector")
# dr.find_element_by_css_selector("input#Test_attribute[type='test email']").send_keys("test attribute selector")
#dr.find_element_by_css_selector("input.inputtext[type='test email']").send_keys("test attribute selector")
# sub-string
dr.find_element_by_css_selector("input[id^='Test_I']").send_keys("test sub-string selector")
# dr.find_element_by_css_selector("input[id$='001']").send_keys("test sub-string selector")
#dr.find_element_by_css_selector("input[id*='ID']").send_keys("test sub-string selector")
# print(dr.find_element_by_css_selector("div[id~='c2']").text)
# print(dr.find_element_by_css_selector("div[class|='five']").text)
# 选择id值包含Test且不包含attribute的属性
dr.find_element_by_css_selector("input[id*='Test']:not([id*='attribute'])").send_keys("test contains sub-string selector")
# 定位子元素
dr.find_element_by_css_selector("div#buttonDiv input").send_keys("test child element")
# 定位多个子元素
print(dr.find_element_by_css_selector("ul#automation li:last-child").text)
print(dr.find_element_by_css_selector("ul#automation li:nth-of-type(2)").text)
# 也可以直接用[attribute=value]进行定位
print(dr.find_element_by_css_selector("[id='two']").text)
print(dr.find_element_by_css_selector("[id^='tw']").text)
Inner-String 选择器
语法：css=tag:contains("inner text")，但是经过试验，不能用，貌似已经弃用这种方法了，会提示错误：invalid selector: An invalid or illegal selector was specified，没办法只能用xpath了
参考：
https://www.w3.org/TR/CSS21/selector.html%23id-selectors
https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_Selectors
https://developer.mozilla.org/en-US/docs/Web/CSS/Specificity
https://code.tutsplus.com/tutorials/the-30-css-selectors-you-must-memorize–net-16048
