How to change profile preference after defining driver?
profile = webdriver.FirefoxProfile()
driver = webdriver.Firefox(firefox_profile=profile)
After some code need to set useragent
profile.set_preference("general.useragent.override", ua)
How to set it without defining new driver?
I believe it’s not possible but I found some workarounds explained in this article, not sure if those approaches are reliable though (or work at all): https://tarunlalwani.com/post/change-profile-settings-at-runtime-firefox-selenium/
As per the current implementation of Selenium once you configure the GeckoDriver with specific Capabilities and initialize the firefox session to open a Browsing Context, you cannot change the capabilities runtime. Even if you are able to retrieve the runtime capabilities still you won't be able to change them back.
So, in-order to change the Firefox User Preference you have to initiate a new WebDriver session.
Note:However, you can change the user-agent for Firefox on each run and you can find a relevant discussion in How to change user agent for Firefox webdriver in Python?
Here is @JimEvans clear and concise comment (as of Oct 24 '13 at 13:02) related to proxy settings capability:
When you set a proxy for any given driver, it is set only at the time WebDriver session is created; it cannot be changed at runtime. Even if you get the capabilities of the created session, you won't be able to change it. So the answer is, no, you must start a new session if you want to use different proxy settings.
You can find a couple of relevant detailed discussions in: