For loop iterating through list of variables

Question

I am looking for a way for a for loop to be able to iterate through a list of variables and be able to use them as variables like this:

>>> a = "original"
>>> b = "original"
>>> c = "original"
>>> d = "original"
>>> for i in [a,b,c,d]:
        i = "change"
>>> print(a,b,c,d)
change change change change

The answer is `exec` if that's actually necessary, but it's highly likely that you don't need that. Why do you want to do this? — zondo, Apr 06 '17 at 00:25
Not going to happen. `[a,b,c,d]` is equal to `["original","original","original","original"]`. It has no memory of the variables `a`, `b`, `c`, and `d`. Why do you want to do this, anyways? This smells like an [XY problem](https://meta.stackexchange.com/questions/66377/what-is-the-xy-problem). — John Kugelman, Apr 06 '17 at 00:25
I think you should probably elaborate on _why_ you want this. Given what you've shown so far, I'm tempted to say that it is impossible in python since strings are immutable and python objects are unaware of what names they are bound to ... — mgilson, Apr 06 '17 at 00:25
Why are you not using a list, instead of individual variables? This smells like poor design. You *could* do it with object **id**s, but that's usually a *bad* idea. — Prune, Apr 06 '17 at 00:25
I don't know what you're trying to do, but it's wrong, and you have an [XY Problem](http://meta.stackexchange.com/questions/66377/what-is-the-xy-problem). — TigerhawkT3, Apr 06 '17 at 00:26

score 1 · Answer 1 · answered Apr 06 '17 at 00:28

1

Your initial code does not work because setting the value of "i" does not actually set the value of variables "a", "b", etc.

a = "original"
b = "original"
c = "original"
d = "original"
list = [a,b,c,d]
for i in range(0,len(list)):
    list[i] = "change"
print(list)

answered Apr 06 '17 at 00:28

dimab0

1,062
8
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Using `list` as a variable name masks the built-in function. – zondo Apr 06 '17 at 00:29
You don't understand, I didn't think that code would actually work, I just used that to show what I wanted to do. @dimab0 – user36456453765745 Apr 06 '17 at 00:30
I realize you knew your code would not work. Does this solve what your intention was? – dimab0 Apr 06 '17 at 00:37

score 0 · Answer 2 · edited May 23 '17 at 10:30

As the comments on the original question point out, this smells a bit and you may want to consider a different way of solving the actual problem. That being said, here's how you might accomplish what you're trying to do:

a = "original"
b = "original"
c = "original"
d = "original"
l = [a, b, c, d]

for idx, val in enumerate(l):
    l[idx] = "change"

print(l)

This results in:

['change', 'change']

Note that print(a) still will result in original as Python strings are immutable

For loop iterating through list of variables

2 Answers2