On Thu, Jan 2, 2014 at 3:35 AM, Steven D'Aprano steve@pearwood.info wrote:
I would have guessed that you could get this working with eval, but if there is such a way, I can't work it out.
It's trivial if you directly invoke eval():
x = 42 def example(): print 'first:', eval('x') y = 'hello world' print 'second:', eval('y') example()
will print
first: 42 second: hello world
Writing Liam's var() as a regular function would require using sys._getframe() and won't access intermediate scopes; something like this would at least find locals and globals:
def var(*args): name = ''.join(map(str, args)) # So var('count', 1) is the same as var('count1') frame = sys._getframe(1) # Caller's frame return eval(name, frame.f_globals, frame.f_locals)
Now this works as desired:
x = 42 def example(): print 'first:', var('x') y = 'hello world' print 'second:', var('y') example()
All in all, agreed this doesn't need to be added to the language, given that it's easy enough() to invoke eval() directly. (And advanced programmers tend to use all kinds of other tricks to avoid the need.)
Two more things, especially for Liam:
(1) There was nothing stupid about your post -- welcome to the Python community!
(2) eval() is much more powerful than just variable lookup; if you write a program that asks its user for a variable name and then pass that to eval(), a clever user could trick your program into running code you might not like to run, by typing an expression with a side-effect as the "variable name". But if you're just beginning it's probably best not to worry too much about such possibilities -- most likely you yourself are the only user of your programs!