How to search for multiple classes in a tag, search by css selector and xpath?

Question

Python

Good afternoon, Parsing Medium and difficulties arose in this matter.
What do I use

from selenium import webdriver
import requests


def md():
    url = 'https://medium.com/@Tacenda/the-universe-is-all-of-space-and-time-spacetime-and-its-contents-9-which-includes-planets-3c9a58475b14'

    driver = webdriver.PhantomJS(executable_path='/usr/local/lib/node_modules/phantomjs-prebuilt/lib/phantom/bin/phantomjs')
    driver.get(url)
    driver.implicitly_wait(5)

    # avatar = driver.find_element_by_css_selector('#_obv\2e shell\2e _surface_1498118264269 > div > main > article > footer > div.u-padding0.u-clearfix.u-backgroundGrayLightest.u-print-hide.supplementalPostContent.js-responsesWrapper > div > div > div.responsesStream.js-responsesStream > div > div > div > div > div.u-clearfix.u-marginBottom10 > div > div > div.postMetaInline-avatar.u-flex0 > a')
    # avatar = driver.find_element_by_xpath('//*[@id="_obv.shell._surface_1498118264269"]/div/main/article/footer/div[5]/div/div/div[4]/div/div/div/div/div[1]/div/div/div[1]/a')
    # avatar = driver.find_elements_by_class_name('link avatar u-baseColor--link')
    avatar = driver.find_elements_by_class_name('link')
    print([i.text for i in avatar])

md()

All commented lines give an error that they cannot find these parameters.
Selector and xpath copied from browser.
Here the question is why it is impossible to find a tag that contains several classes?
I looked on the network that they add .link.avatar , but it did not help.
Looking for a class in a tree house

'link avatar u-baseColor--link' in driver.page_source

Returns true
Here's the part I need to parse, namely the href and img src tags

<a class="link avatar u-baseColor--link" href="https://medium.com/@Tacenda" data-action="show-user-card" data-action-value="17f98bbae51d" data-action-type="hover" data-user-id="17f98bbae51d" dir="auto"><img src="https://cdn-images-1.medium.com/fit/c/36/36/1*Jtm9sTbkCLI_0A0AadvVzw.jpeg" class="avatar-image u-size36x36 u-xs-size32x32" alt="Go to the profile of Adriano Celentano"></a>

Before that, I used bs4, lxml, everything was easy, you write a tag, a class and voila, everything was found, turned to the attributes and got it.
How to do everything right here? This is my second day doing this.

Answer 1

.link.avatar.u-baseColor--link

Here is a CSS selector that returns an array of 7 elements
. Take any (they are the same). Read the values ​​of the href attribute and find the nested img in it
There is an easy way to match CSS selectors:

1. Find an element on a page
   
2. RMB -> Inspect element
   
3. The page with the source code will open. The desired item will be highlighted.
   
4. See how you can locally set a unique css selector
   
5. Go to browser console
   
6. Write "$$('your css selector')"
   
7. If an array with one element is returned, you have chosen a convenient selector