Python Regular Expressions: Capture

>>> m = re.search(r'^(\d{3,4}-)?(\d{7,8})$','020-82228888')
>>> m.group(0)
'020-82228888'
>>> m.group(1)
'020-'
>>> m.group(2)
'82228888'

>>> re.findall(r'(\d{3,4}-)?(\d{7,8})','020-82228888\n0357-4227865') 
[('020-', '82228888'), ('0357-', '4227865')]

>>> re.findall(r'(?:\d{3,4}-)?\d{7,8}','020-82228888\n0357-4227865') 
['020-82228888', '0357-4227865']
>>> re.findall(r'(?:\d{3,4}-)?\d{7,8}','020-82228888\n4227865')  
['020-82228888', '4227865']

>>> sentence = """You said "why?" and I say "I don't know"."""
>>> re.findall(r'["\'](.*?)["\']', sentence)
['why?', 'I don']
>>> re.findall(r'(["\'])(.*?)\1', sentence)
[('"', 'why?'), ('"', "I don't know")]

>>> sentence = "from 12/22/1629 to 11/14/1643"
>>> re.sub(r&#39;(?P<month>\d{2})/(?P<day>\d{2})/(?P<year>\d{4})&#39;, r&#39;\g<year>-\g<month>-\g<day>&#39;, sentence) 
&#39;from 1629-12-22 to 1643-11-14&#39;

>>> sentence = """You said "why?" and I say "I don't know"."""
>>> re.findall(r&#39;(?P<quote>["\&#39;])(.*?)\g<quote>&#39;, sentence)  
[]
>>> re.search(r&#39;(?P<quote>["\&#39;])(.*?)\g<quote>&#39;, sentence)   
>>> re.search(r&#39;(?P<quote>["\&#39;])(.*?)\1&#39;, sentence)  
<_sre.SRE_Match object; span=(9, 15), match=&#39;"why?"&#39;>
>>> re.search(r&#39;(?P<quote>["\&#39;])(.*?)\1&#39;, sentence).groupdict()
{&#39;quote&#39;: &#39;"&#39;}