Python thing that doesn't work in Sage, works in pure Python

Question

In sage -python:

>>> import re
>>> ST = "foobarsws"
>>> matches = re.match("(?:foo)?(bar)?(sws)?",ST)
>>> matches.groups()
('bar', 'sws')
>>> matches.group(0)
'foobarsws'
>>> matches.group(1)
'bar'
>>> matches.group(2)
'sws'

In Sage:

sage: import re
sage: ST = "foobarsws"
sage: matches = re.match("(?:foo)?(bar)?(sws)?",ST)
sage: matches.groups()
('bar', 'sws')
sage: matches.group()
'foobarsws'
sage: matches.group(0)
IndexError: no such group
sage: matches.group(1)
IndexError: no such group
sage: matches.group(2)
IndexError: no such group

Any ideas?

Accepted Answer

Never mind.

sage: matches.group(int(1))
'bar'

Leaving this up for those who might stumble. I'll try to think of a better title for the question so people find it.

This seems bad, though. I suppose there isn't any way to notice when we are using "pure Python" commands and for the preparser to at least try not doing the whole Integer thing if it gets an Error of some kind? Maybe that would lead to more chaos than we'd like.

Answer 2

For others that stumble across this question, you can turn the Sage preparser off by calling preparser(False). Then the code above works just fine at the Sage command line:

sage: preparser(False)
sage: import re
sage: ST = "foobarsws"
sage: matches = re.match("(?:foo)?(bar)?(sws)?",ST)
sage: matches.groups()
('bar', 'sws')
sage: matches.group()
'foobarsws'
sage: matches.group(0)
'foobarsws'
sage: matches.group(1)
'bar'

Python thing that doesn't work in Sage, works in pure Python

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