Python Selenium.WebDriverWait determines whether an element exists
1, Determine whether the element exists
Selenium does not have a direct method to judge whether an element exists, so we can only write a special function or method through some existing methods. Here I summarize three methods for your reference, which can be selected according to their advantages and disadvantages and application scenarios
As for the function of judging whether elements exist, I think there are mainly two aspects:
- First, judge whether the element exists before operating it, which can effectively avoid error reporting
- Another is to judge whether the element exists, and then execute some code logic only if it exists, such as operating on other elements in the page
In the following example, I will use an xpath expression or id to capture an element
2, Exception capture
Exception capture is the first method that can be thought of. If the element does not exist when obtaining the element, a NoSuchElementException exception that does not find the element will be thrown.
Before you start, you need to know that Selenium places all exceptions in Selenium common. Under exceptions, you need to import the file from Selenium common import exceptions
def iselement(browser, xpaths):
"""
The basic implementation determines whether the element exists
:param browser: Browser object
:param xpaths: xpaths expression
:return: Does it exist
"""
try:
browser.find_element_by_xpath(xpaths)
return True
except exceptions.NoSuchElementException:
return False
If we don't just judge whether the element exists, we also need to process the element when it exists. According to the above code, we need to execute the capture behavior twice, the first is to judge and the second is to operate on the element. We can optimize it so that it can be captured at one time.
If you just want to get the text in the element, you can write it this way. You only need to improve it on the original basis
def iselement(browser, xpaths, istest=False):
"""
The implementation determines whether the element exists
:param browser: Browser object
:param xpaths: xpaths expression
:param istest: If yes True,If the element exists, the returned content will be the element text content
:return: Does it exist
"""
try:
target = browser.find_element_by_xpath(xpaths)
except exceptions.NoSuchElementException:
return False
else:
if istest:
return target.text
return True
If you need to perform other operations, you can directly return the element object
def get_element(browser, xpaths):
"""
Determine whether an element exists and get the element object
:param browser: Browser object
:param xpaths: xpaths expression
:return: Element object or empty
"""
try:
target = browser.find_element_by_xpath(xpaths)
except exceptions.NoSuchElementException:
return
else:
return target
For exceptions that show waiting, it is exceptions TimeoutException
3, Multi element capture null judgment
Selenium also has methods for finding multiple elements at once, which return a list
| Single element | Multiple elements | describe |
|---|---|---|
| find_element_by_id | nothing | Find element by ID |
| find_element_by_name | find_elements_by_name | Find element by Name |
| find_element_by_xpath | find_elements_by_xpath | Find elements through XPath |
| find_element_by_link_text | find_elements_by_link_text | Get hyperlink from link text |
| find_element_by_partial_link_text | find_elements_by_partial_link_text | Get hyperlink from link text |
| find_element_by_tag_name | find_elements_by_tag_name | Find element by tag name |
| find_element_by_class_name | find_elements_by_class_name | Locate the element by Class name |
| find_element_by_css_selector | find_elements_by_css_selector | Find elements through CSS selectors |
For elements that cannot be obtained, an empty list will be returned. According to the principle of whether it is empty, you can judge whether the element exists
def iselement(browser, xpaths, istest=False):
"""
The implementation determines whether the element exists
:param browser: Browser object
:param xpaths: xpaths expression
:param istest: If yes True,If the element exists, the returned content will be the element text content
:return: Does it exist
"""
target = browser.find_elements_by_xpath(xpaths)
if not target:
return False
if istest:
return target[0].text
return True
def get_element(browser, xpaths):
"""
Determine whether an element exists and get the element object
:param browser: Browser object
:param xpaths: xpaths expression
:return: Element object or empty
"""
target = browser.find_elements_by_xpath(xpaths)
if target:
return target[0]
4, Page source code acquisition
This method is not very practical, but it can be considered for pages whose target content has been loaded
The principle is very simple, that is to pass the source code of the current page through browser page_ The source attribute is obtained, and then the source code is submitted to these libraries for processing, further data judgment and extraction
from lxml import etree from bs4 import BeautifulSoup
Page parsing using BeautifulSoup
soup = BeautifulSoup(browser.page_source, "html.parser")
Page parsing using etree
tree = etree.HTML(browser.page_source)
reference material 💌
- Official manual
Heartfelt thanks 💖