__getitem__ was added to match objects as a resolution of issue24454.

Wouldn't it be nice to also have `__contains__` and `get` methods for match objects? Is it even feasible to implement them in neat way?

They should work similar to dictionaries, i.e:

```
match = re.match('(?P<a>a)', 'a')
match.get('b')  # should return None
match.get(1)  # should return 'a'
'a' in match # True
'b' in match # False
```

I predicted that that change will open a can of worms.

The match object is not a dictionary. I don't see a need in new methods. The get() method you propose looks virtually the same as the group() method. "'a' in match" is virtually the same as "match.get('a') is not None".

+1 for m.get(key[, default])
-1 for __contains__

The get() makes logical sense and it is perfectly reasonable to want a default value for a missing group.

The contains idea makes less sense and is problematic on several fronts.  "'a' in match" only works if the match object is not None but it looks like a traditional membership test.  Also, I think it will lead to confusion over whether contains is testing the key or the value:

  m = re.match('(?P<a>[ab])', 'a')
  'a' in m    # True
  'b' in m    # False

  m = re.match('(?P<a>[ab])', 'b')
  'a' in m    # True  
  'b' in m    # False

  m = re.match('(?P<a>[ab])', 'c')
  'a' in m    # TypeError
  'b' in m    # TypeError

IMO, it is better to leave out __contains__ and let people just use groupdict() where they know for sure that normal dict semantics apply.