Evgeniy _

import ast
from selenium import webdriver

wd = webdriver.Firefox()
wd.get('https://goo.gl/knrjOl')
all_pics = wd.find_elements_by_xpath("//div[@class='rg_meta']")
try:
    for pic in all_pics:
        a = ast.literal_eval(wd.execute_script("return arguments[0].innerHTML", pic))
        if "ou" in a.keys():
            print a["ou"]
finally:
    wd.close()
    wd.quit()

Необходимо получить подстроку, которая чаще остальных встречается в строке?

a = [("a", 2), ("c", 5), ("b", 6)]
max(a, key=lambda x: x[1])[0]
=> b

если просто отсортировать по value (max -> min):

sorted(a, key=lambda x:x[1], reverse = True)

=> [('b', 6), ('c', 5), ('a', 2)]

selenium-python.readthedocs.org/api.html#selenium....

key_down(value, element=None)

Sends a key press only, without releasing it.
Should only be used with modifier keys (Control, Alt and Shift).

Args:

value: The modifier key to send. Values are defined in Keys class.
element: The element to send keys. If None, sends a key to current focused element.

Example, pressing ctrl+c:

ActionChains(driver).key_down(Keys.CONTROL).send_keys('c').key_up(Keys.CONTROL).perform()

from operator import sub
result = map(sub, b, a)

Предположу, что тебе мешает некий Кирилл в path )

UnicodeDecodeError: 'utf-8' codec can't decode byte 0xc1 in position 0: invalid start byte
C:\Users\Кирилл\AppData\Local\Programs\Python\Python35\lib\socket.py

("//div[starts-with(@class,'item selected')]//span")