As pointed out by Guido in https://bugs.python.org/issue43555, we switched to making the column offsets for SyntaxError be 1-indexed consistently in https://bugs.python.org/issue34683

The rationale is explained by Guido and expanded upon in follow up comments here: https://github.com/python/cpython/pull/9338#pullrequestreview-155989089 

This property however was not actually ever added to SyntaxError's documentation: https://docs.python.org/3/library/exceptions.html#SyntaxError

New changeset b2a91e0c9ee18b50cc86b21211c2258520a9f5d0 by Ammar Askar in branch 'master':
bpo-43705: Document that SyntaxError's offsets are 1-indexed (GH-25153)
https://github.com/python/cpython/commit/b2a91e0c9ee18b50cc86b21211c2258520a9f5d0

New changeset 06653f8d15a8a84ee0f43f739704a9a63c27de54 by Miss Islington (bot) in branch '3.8':
bpo-43705: Document that SyntaxError's offsets are 1-indexed (GH-25153)
https://github.com/python/cpython/commit/06653f8d15a8a84ee0f43f739704a9a63c27de54

New changeset 63c69440c7adb0de1d191a8d3d100b335d5c2f81 by Miss Islington (bot) in branch '3.9':
bpo-43705: Document that SyntaxError's offsets are 1-indexed (GH-25153)
https://github.com/python/cpython/commit/63c69440c7adb0de1d191a8d3d100b335d5c2f81

Should we mention that the 4 attributes are also available as a 4-tuple that is the 2nd item of the args tuple, after the message?  Doing so will help when illustrating the following.

For syntax errors in f-string fields, the expanded doc is still incomplete/erroneous.  The text attribute is the replacement expression wrapped in parentheses (or with {} replaced by ()), with \n added; the column is the (1-based) offset within that constructed source.

>>> try:
	compile("f'Bad {a b} field'", '', 'exec')
except SyntaxError as e:
	print(e.args)

('f-string: invalid syntax', ('', 1, 4, '(a b)\n'))

This was brought to my attention a week or so ago because IDLE still thinks that 4 refers to the  'a' of 'Bad' and marks it is the error location.  I had to deduce the rule from examples.

Whether for this issue or a new one, I am thinking of something like the following.
---

For syntax error instances, the args attribute is (error-message, details-tuple).  The str returns only the error message.  For convenience, the four details are also available as separate attributes.

<new list as is>

For errors in f-string fields, the message is prefixed by "f-string:" and the offset is the offset in a text constructed from the replacement expression.  For example, compiling f'Bad {a b} field' results in the following args attribute: ('f-string: invalid syntax', ('', 1, 4, '(a b)\n')).

I think it okay to require the reader to match '{a b}' and '(a b)\n' to deduce the transformation rule.  Messages other than 'invalid syntax', like 'closing parenthesis ...' get the same prefix.  Anything Python specific can be labelled as such.

Aah thanks for pointing that out Terry, I didn't realize f-strings have different semantics for SyntaxError. Would you mind making a separate issue for that, I'll look into making the documentation for it clearer after I get a chance to investigate.