eval() and local variables

[Peter Luciak]

Hi,
I need to do something like this:

def my():
a,b=1,2
func = "lambda x: a*x+b"
map(eval(func),[1,2,3])

my()

NameError: global name 'a' is not defined

Why do I have to make a,b global for this to work?

Thanks,
P.

 

[Peter Otten]

Hi,
I need to do something like this:

def my():
a,b=1,2
func = "lambda x: a*x+b"
map(eval(func),[1,2,3])

my()

NameError: global name 'a' is not defined

Why do I have to make a,b global for this to work?

You don't:
.... a, b = 1, 2
.... return map(eval("lambda x: a*x+b", locals()), [1,2,3])
....[3, 4, 5]

That makes my's local variables eval's globals.
However, it's not clear to me why you need eval() at all:
.... a, b = 1, 2
.... func = lambda x: a*x+b
.... return map(func, [1,2,3])
....[3, 4, 5]

Peter