[Tutor] corresponding command in Python to "eval" in Matlab

Kent Johnson kent37 at tds.net
Sun Oct 7 22:36:26 CEST 2007

Eric Brunson wrote:
> However, I didn't actually answer your question.
> As Kent has already mentioned, eval is quite dangerous in python and to 
> be avoided when possible.  I think it would be safer to do something 
> like this:
> l = locals()
> for x, y in zip( varlist, data ):
>     l[x] = y
> or, more tersely:
> [ locals()[x] = y for x, y in zip( varlist, data ) ]
> This will accomplish what you're trying to do, but a dict really gives  
> you greater functionality than assigning to local variables.

This will only work at global scope where locals() is globals() and 
writable. In function scope assigning to locals()[...] does not change 
the local namespace:

In [27]: def foo():
    ....:     locals()['x'] = 1
    ....:     print x
In [28]: foo()
Traceback (most recent call last):
   File "<ipython console>", line 1, in <module>
   File "<ipython console>", line 3, in foo
<type 'exceptions.NameError'>: global name 'x' is not defined


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