You need to access the page_source property:

from selenium import webdriver

browser = webdriver.Firefox()
browser.get("http://example.com")

html_source = browser.page_source
if "whatever" in html_source:
    # do something
else:
    # do something else

Here is a simple code all it does is it opens the url and gets the length page source and waits for five seconds and will get the length of page source again.

if __name__=="__main__":
    browser = webdriver.Chrome()
    browser.get("https://codefights.com/tournaments/Xph7eTJQssbXjDLzP/A")
    initial = len(browser.page_source)
    print(initial)
    time.sleep(5)
    new_source = browser.page_source
    print(len(new_source)

see the output: 15722 48800

you see that the length of the page source increases after a wait? you must make sure that the page is fully loaded before getting the source. But this is not a proper implementation since it blindly waits.

Here is a nice way to do this, The browser will wait until the element of your choice is found. Timeout is set for 10 sec.

if __name__=="__main__":
    browser = webdriver.Chrome()
    browser.get("https://codefights.com/tournaments/Xph7eTJQssbXjDLzP/A")
    try:
        WebDriverWait(browser, 10).until(EC.presence_of_element_located((By.CSS_SELECTOR, '.CodeMirror > div:nth-child(1) > textarea:nth-child(1)')))  # 10 seconds delay
        print("Result:")
        print(len(browser.page_source))
    except TimeoutException:
        print("Your exception message here!")

The output: Result: 52195

Reference:

https://stackoverflow.com/a/26567563/7642415

http://selenium-python.readthedocs.io/locating-elements.html

Hold on! even that wont make any guarantees for getting full page source, since individual elements are loaded dynamically. If the browser finds the element it moves on. So make sure you find the proper element to make sure the page has been loaded fully.

P.S Mine is Python3 & webdriver is in my environment PATH. So my code needs to be modified a bit to make it work for Python 2.x versions. I guess only print statements are to be modified.