[wxPython-users] Re: OT - how to create variables from a cvs file?

[Mel Wilson]

Christian wrote:
> jmf wrote:
>> locals() beeing the dict containing the vars...
>>
>>>>> li = ['field1', 'field2', 'field3']
>>>>> for e in li:
>>        locals()[e] = None
>>>>> print field1
>> None
>>>>> print field2
>> None
>>>>> print field3
>> None
> 
> I read somewhere that both globals() and locals() are not meant for writing. So
> this might or might not work always.

AFAIK, the dictionary returned by globals() is used to look up global 
variables, and adding an entry will add a variable.

However, the dictionary returned by locals() is usually a made-up 
dictionary which gives access to local variables, but isn't consulted 
by the Python interpreter.  Inside functions, local variables are 
accessed through a pre-compiled array of references (the decompiled 
code for a small function will show this) so changing a locals() 
dictionary changes nothing.

Outside any function, a call to locals() returns a reference to the 
same dictionary returned by globals(), so the example above works.
Consider
Python 2.4.2 (#1, Jan 23 2006, 21:24:54)
[GCC 3.3.4] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> def f():
...   d = locals()
...   d['a'] = 1
...   d['b'] = 2
...   print a, b
...
>>> f()
Traceback (most recent call last):
   File "<stdin>", line 1, in ?
   File "<stdin>", line 5, in f
NameError: global name 'a' is not defined
>>>                                           



	Mel.