On 2018-07-14 10:39, Jonathan Fine wrote:
Hi Ken
Thank you for your clear subject line. As you probably already know, in
Python, assignments are not expressions, and so we can't write
if (a=get()):
# do something with a
One reason for this is, perhaps, that "Explicit is better than implicit"
(as in The Zen of Python, via "import this").
Your last example of the intended semantics is
b = a * (import math).tan(math.radians(45))
which demonstrate that you intend the statement
a = (import math)
to have the side effect of assigning a value to the identifier 'math'.
I'm concerned that your intended semantics are similar to "assignment as
an expression", and so wouldn't fit in well with the rest of Python.
More concretely, when reading a module I expect to see all the imports
at the top, much like a recipe starts with a list of ingredients.
It may be that the documentation regarding import and __import__ can be
improved, and that there's a practical problem behind your experience
that __import__ is cumbersome and takes space.
With PEP 572 you would be able to write:
b = a * (math := __import__('math')).tan(math.radians(45))
but I don't think that would be an improvement over:
import math
b = a * math.tan(math.radians(45))
So -1.
[snip]
On Sat, Jul 14, 2018 at 9:24 AM, Ken Hilton <[email protected]
<mailto:[email protected]>> wrote:
Hi all,
Just a curious idea I had. The subject says it all. "import" is
currently a statement, which means it cannot be used inside anything
else. Currently, the only way to import a module inside an
expression is to use the __import__ function, which is both
cumbersome and takes up more space (which is disadvantageous in
things like code golf).
I propose making "import" an expression, thus allowing the syntactic
sugar of "import module" -> "__import__('module')" to be graduated
to the expression level. Because of operator precedence, I suspect
that in most cases one would need to surround the expression with
parentheses.
An additional effect that is not seen with using __import__ is that
the module's name is bound to the current scope the way it is with a
normal import statement.
Examples of where this could be used:
Importing on the fly to generate one value:
secret = (import random).randint(1, 100)
Quick use of itertools in generator expressions:
(i * i for i in (import itertools).accumulate(generate_numbers()))
Re-using a function from a module after importing it in an expression:
b = a * (import math).tan(math.radians(45)) #math.radians is
valid because (import math) binds "math" to the current scope
What are your thoughts?
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