On Sat, 23 Jun 2007 19:58:32 +0000, vasudevram wrote:
>
> Hi group,
>
> Question: Do eval() and exec not accept a function definition? (like
> 'def foo: pass) ?
eval() is a function, and it only evaluates EXPRESSIONS, not code blocks.
eval("2+3") # works
eval("x - 4") # works, if x exists
eval("print x") # doesn't work
exec is a statement, and it executes entire code blocks, including
function definitions, but don't use it. Seriously.
ESPECIALLY don't use it if you are exec'ing data collected from untrusted
users, e.g. from a web form.
> I wrote a function to generate other functions using something like
> eval("def foo: ....")
> but it gave a syntax error ("Invalid syntax") with caret pointing to
> the 'd' of the def keyword.
You don't need eval or exec to write a function that generates other
functions. What you need is the factory-function design pattern:
def factory(arg):
def func(x):
return x + arg
return func
And here it is in action:
>>> plus_one = factory(1)
>>> plus_two = factory(2)
>>> plus_one(5)
6
>>> plus_two(5)
7
--
Steven.
--
http://mail.python.org/mailman/listinfo/python-list
