How can I get the first child?
London
York
With modern versions of bs4 (certainly bs4 4.7.1+) you have access to :first-child css pseudo selector. Nice and descriptive. Use soup.select_one if you only want to return the first match i.e. soup.select_one('.cities div:first-child').text. It is considered good practice to test is not None before using .text accessor.
from bs4 import BeautifulSoup as bs
html = '''
London
York
'''
soup = bs(html, 'lxml') #or 'html.parser'
first_children = [i.text for i in soup.select('.cities div:first-child')]
print(first_children)