change vars in place w/loop or list comprehension

[ken....@dnr.state.mn.us]

I am a python newbie, and am grappling with a fundamental concept. I
want to
modify a bunch of variables in place. Consider the following:

>>> a = 'one'
>>> b = 'two'
>>> c = 'three'
>>> list = [a, b, c]
>>> for i in range(len(list)):
... list[i] = list[i].upper()
...
>>> [a, b, c] = list
>>> a
'ONE'

or, better:

>>> a = 'one'
>>> b = 'two'
>>> c = 'three'
>>> [a, b, c] = [s.upper() for s in [a, b, c]]
>>> a
'ONE'

Both of these accomplish what I'm after; I prefer the second for its
brevity.
But either approach requires that I spell out my list of vars-to-alter
[a, b, c] twice. This strikes me as awkward, and would be difficult
with longer lists. Any suggestions for a better way to do this?

--Ken

[Jatinder Singh]

Hi
what u can do over here is
add a,b,c... in a list e.g. list.append(vars..)
and then use the statement
newlist = map(lambda x:x.upper(),list)
Now ur newlist will contain the modified list.
HOPE THIS THE BETTER SOLUTION TO UR PROBLEM

Quoting ken....@dnr.state.mn.us:

> --
> http://mail.python.org/mailman/listinfo/python-list
>

--
Regards,
Jatinder Singh

“ Everyone needs to be loved... especially when they do not deserve it.”

[Raymond Hettinger]

> >>> a = 'one'
> >>> b = 'two'
> >>> c = 'three'
> >>> [a, b, c] = [s.upper() for s in [a, b, c]]
> >>> a
> 'ONE'
>
> Both of these accomplish what I'm after; I prefer the second for its
> brevity. But either approach requires that I spell out my list of
> vars-to-alter [a, b, c] twice. This strikes me as awkward, and
> would be difficult
> with longer lists.

seq = a, b, c
a, b, c = seq = [s.upper() for s in seq]

[Peter Hansen]

ken....@dnr.state.mn.us wrote:
> I am a python newbie, and am grappling with a fundamental concept. I
> want to
> modify a bunch of variables in place. Consider the following:
>

[snip]

>>>>a = 'one'
>>>>b = 'two'
>>>>c = 'three'
>>>>[a, b, c] = [s.upper() for s in [a, b, c]]
>

> Both of these accomplish what I'm after; I prefer the second for its
> brevity.
> But either approach requires that I spell out my list of vars-to-alter
> [a, b, c] twice. This strikes me as awkward, and would be difficult
> with longer lists. Any suggestions for a better way to do this?

While the real question is why you think you need to modify a bunch of
variables in place**, here's one solution to the immediate problem:

for name in 'a b c'.split():
globals()[name] = globals()[name].upper()

That, of course, will work only if they really are globals, and not if
they are local variables inside a function. If that's the case, you
really want to rethink this anyway (or use Raymond's approach, though it
still appears to require spelling out your list of names twice).

** Why you might not want to do this at all:

It's very rare in real code to need to work with a large number of
variables as a set like that. More generally you should probably be
storing the strings in something like a list and manipulating them
there. This would look like this:

shtuff = ['a', 'b', 'c']
for i,item in enumerate(shtuff):
shtuff[i] = item.upper()

Or, even more likely:

newList = []
for item in shtuff:
newList.append(item.upper())

shtuff = newList

If you think you really need to do this anyway, consider posting an
example of real code from the program you are trying to write,
explaining the actual use case, and we can analyze the real situation
instead of debating contrived examples.

-Peter