Got it! The clue was on selenium.webdriver.remote.webelement — Selenium 3.14 documentation.
WebElements have the properties .size and .location. Both are of type dict.
driver = webdriver.Firefox()
e = driver.find_element_by_xpath("//someXpath")
location = e.location
size = e.size
w, h = size['width'], size['height']
print(location)
print(size)
print(w, h)
Output:
{'y': 202, 'x': 165}
{'width': 77, 'height': 22}
77 22
They also have a property called rect which is itself a dict, and contains the element’s size and location.