Georg Brandl wrote:
Am 21.10.2010 16:06, schrieb Benjamin Peterson:
Raymond Hettinger <raymond.hettinger@...> writes:
One of the use cases for named tuples is to have them be automatically created
from a SQL query or CSV header.
Sometimes (but not often), those can have a huge number of columns. In Python
2.x, it worked just fine -- we
had a test for a named tuple with 5000 fields. In Python 3.x, there is a
SyntaxError when there are more than
255 fields.
I'm not sure why you think this is new. It's been true from at least 2.5 as far as I can see.
You must be talking of a different restriction. This snippet works fine in 2.7, but raises a SyntaxError in 3.1:
exec("def f(" + ", ".join("a%d" % i for i in range(1000)) + "): pass")
The AST code in 2.7 raises this error for function/method calls only. In 3.2, it also raises the error for function/method definitions.
Looking at the AST code, the limitation appears somewhat arbitrary. There's no comment in the code suggesting a reason for the limit and it's still possible to pass in more arguments via *args and **kws - but without the built-in argument checking.
Could someone provide some insight ?
Note that it's not uncommon to have more than 255 possible function/method arguments in generated code, e.g. in database abstraction layers.
Thanks,