Selenium webdriver: How do I find ALL of an element's attributes?

It is not possible using a selenium webdriver API, but you can execute a javascript code to get all attributes:

driver.execute_script('var items = {}; for (index = 0; index < arguments[0].attributes.length; ++index) { items[arguments[0].attributes[index].name] = arguments[0].attributes[index].value }; return items;', element)

Demo:

>>> from selenium import webdriver
>>> from pprint import pprint
>>> driver = webdriver.Firefox()
>>> driver.get('https://stackoverflow.com')
>>> 
>>> element = driver.find_element_by_xpath('//div[@class="network-items"]/a')
>>> attrs = driver.execute_script('var items = {}; for (index = 0; index < arguments[0].attributes.length; ++index) { items[arguments[0].attributes[index].name] = arguments[0].attributes[index].value }; return items;', element)
>>> pprint(attrs)
{u'class': u'topbar-icon icon-site-switcher yes-hover js-site-switcher-button js-gps-track',
 u'data-gps-track': u'site_switcher.show',
 u'href': u'//stackexchange.com',
 u'title': u'A list of all 132 Stack Exchange sites'}

For completeness sake, an alternative solution would be to get the tag's outerHTML and parse the attributes using an HTML parser. Example (using BeautifulSoup):

>>> from bs4 import BeautifulSoup
>>> html = element.get_attribute('outerHTML')
>>> attrs = BeautifulSoup(html, 'html.parser').a.attrs
>>> pprint(attrs)
{u'class': [u'topbar-icon',
            u'icon-site-switcher',
            u'yes-hover',
            u'js-site-switcher-button',
            u'js-gps-track'],
 u'data-gps-track': u'site_switcher.show',
 u'href': u'//stackexchange.com',
 u'title': u'A list of all 132 Stack Exchange sites'}

The following gets a list of all attributes and their (sometimes translated to strings) values for me, using the PhantomJS or Chrome driver at least:

elem.get_property('attributes')[0]

To just get the names:

x.get_property('attributes')[0].keys()

You can find using element.get_property() method.

from selenium import webdriver
from selenium.webdriver.common.by import By

driver = webdriver.Chrome()
driver.get("https://www.ultimateqa.com/complicated-page/")

logo = driver.find_element(By.XPATH, "//img[@id='logo']")
attrs=[]
for attr in logo.get_property('attributes'):
    attrs.append([attr['name'], attr['value']])
print(attrs)

Output:

[['src', 'https://www.ultimateqa.com/wp-content/uploads/2019/01/horizontal_on_transparent_by_logaster-2.png'], ['alt', 'Ultimate QA'], ['id', 'logo'], ['data-height-percentage', '100'], ['data-actual-width', '912'], ['data-actual-height', '410']]