Looking at problems from a fresh perspective: analyzing selenium principle from the perspective of Python

Selenium Workflow

Selenium working principle

The client and server are actually connected through http Protocol to communicate , The interface document of the server can be referred to ：

https://github.com/SeleniumHQ/selenium/wiki/JsonWireProtocol#sessionsessionidelement

The client passes in the request mode according to the requirements of the server interface 、 request url And request data , And then send http request , After receiving the request, the server drives the browser to execute the command .

selenium Actually, the request functions of various operation interfaces have been encapsulated , Users only need to pass in data through the specified method .

Such as get、click、find_element It actually encapsulates the whole http Method of request process .

That is, the tester only needs to call the corresponding method according to the functional requirements and pass the parameters , In the end by the selenium After assembling the request information, send the request .

so , You can skip it selenium, By myself requests The module build request information is sent to the driver , So as to drive the browser to perform relevant operations .

From the perspective of source code Selenium principle

explain

Following example , With Python、Chrome The driver 、Chrome Browser expansion instructions .

adopt Selenium Implement workflow

# start-up chrome browser
driver = webdriver.Chrome()
# Visit Baidu website
driver.get("http://www.baidu.com")
# Find the input box element
ele = driver.find_element_by_id("kw")
# Enter in the input box “selenium”
ele.send_keys("selenium")
# Find Baidu button
ele = driver.find_element_by_id("su")
# Click Baidu button
ele.click()

Selenium The source code parsing

① driver = webdriver.Chrome()

start-up chromedriver The driver , After starting, it can pass http://ip:port Access driver .

adopt execute Method , structure “ Create a new session ” Interface request information , And send the http request , Return to session id.

Request mode ：POST

Request address ：http://localhost:post/session

Request data ：

data = {"desiredCapabilities":{
"browserName": "chrome",
"version":"85.0.4183.83",
"platform":"WINDOWS"}
}

② driver.get(“http://www.baidu.com”)

adopt execute Method , Press get Command interface information construction http Request information , And send the http request .

Request mode ：POST

Request address ：http://localhost:post/session/$sessionId/url（sessionId For session id, from ① In order to get ）

Request data ：

{"url": "http://www.baidu.com"}

③ driver.find_element_by_id(“kw”)

adopt execute Method , Press find_element_by_id Command interface information construction http Request information , And send the http request .

Request mode ：POST

Request address ：http://localhost:post/session/$sessionId/element（sessionId For session id, from ① In order to get ）

Request data ：

{"using":"id","value":"kw"}

④ ele.send_keys(“selenium”)

adopt execute Method , Press send_keys Command interface information construction http Request information , And send the http request .

Request mode ：POST

Request address ：http://localhost:post/session/$sessionId/element/$id/value（sessionId For session id, from ① In order to get ,id For the elements id, from ③ obtain ）

Request data ：

{"value": ["selenium"]}

⑤ ele.click()

adopt execute Method , Press click Command interface information construction http Request information , And send the http request .

Request mode ：POST

Request address ：http://localhost:post/session/$sessionId/element/$id/click（sessionId For session id, from ① In order to get ,id For the elements id, from ③ obtain ）

Request data ： nothing

adopt requests Module operation verification

Code implementation

 # TODO Access to the domain name
base_url = "http://localhost:9515"
# TODO Create a session
url = base_url + "/session"
data = {
"desiredCapabilities":{
"browserName": "chrome",
"version":"85.0.4183.83",
"platform":"WINDOWS"
}
}
res = request("POST",url,json=data)
session_id = res.json()["sessionId"] # Return to session id
sleep(2)
# TODO send out get command - Visit a website
url = base_url + "/session/{}/url".format(session_id)
data = {
"url": "http://www.baidu.com"
}
res = request("POST",url,json=data)
# TODO send out find_element command - Look for the element
url = base_url + "/session/{}/element".format(session_id)
data = {
"using":"id",
"value":"kw"
}
res = request("POST",url,json=data)
ele = jsonpath(res.json(),"$..ELEMENT")[0] # Returns the element id
# TODO send out send_keys command - Input content
url = base_url + "/session/{}/element/{}/value".format(session_id,ele)
data = {
"value": ["selenium"]
}
res = request("POST",url,json=data)
# TODO send out find_element command - Look for the element
url = base_url + "/session/{}/element".format(session_id)
data = {
"using":"id",
"value":"su"
}
res = request("POST",url,json=data)
ele = jsonpath(res.json(),"$..ELEMENT")[0] # Returns the element id
# TODO send out click command - Element click
url = base_url + "/session/{}/element/{}/click".format(session_id,ele)
res = request("POST",url)

Running results

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