On Thu, 16 Sep 2010 01:35:17 pm David Hutto wrote:
> print("a is", a)
> or
> from future import *
Neither of those lines are correct. Given (say) a=42, in Python 2.6 the
first line will print the tuple:
("a is", 42)
while in Python 3.1 it will print the string:
a is 42
Note the extra punctuation in the first version. For a quick-and-dirty
script, you might not care about that, so passing tuples to print in
2.x is a reasonably simple work-around, but they are not the same.
On the other hand, the second line does behave the same in both Python
2.6 and 3.1:
>>> from future import *
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ImportError: No module named future
It might be the same, but I'm pretty sure it's not useful.
What you are thinking of is the special module __future__ with leading
and trailing double-underscores. __future__ is special -- the line
from __future__ import ...
(where ... is one or more feature) tells the Python compiler to change
behaviour. If you use a "from __future__ import" line, it MUST be the
first executable line in a module or script. It's okay for it to follow
blank lines, comments or a doc-string, but it must be before any other
line of Python code.
In the case of Python 2.6 you can execute:
from __future__ import print_function
to turn print into a function like in 3.1.
However, you can't use the asterisk form:
>>> from __future__ import *
File "<stdin>", line 1
SyntaxError: future feature * is not defined
--
Steven D'Aprano
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