Python convert String to Variable in the loop

Question

I would like to do something like this:

x = 0
y = 3

TEST0 = 10 
TEST1 = 20 
TEST2 = 30

while x < y:
    result = exec('TEST{}'.format(x))
    print(result)
    x += 1

And have the output:

10
20
30

Somehow convert TEST{variable} to the actual variable, or what is the way to do it?

Currently, I have result as:

None
None
None

Do you have a good reason for not using a list with items 10, 20, and 30? — GordonAitchJay
– GordonAitchJay, Commented Mar 27, 2020 at 9:02
Instead of calling exec(), call eval() to get the result you expect. Having said that, you almost certainly don't want to do it that way. Use a more appropriate data type. — GordonAitchJay
– GordonAitchJay, Commented Mar 27, 2020 at 9:05

Thomas · Accepted Answer · 2020-03-27 09:02:37Z

6

Welcome to Python! What you need is a list:

x = 0
y = 3

TEST = [10, 20, 30]

while x < y:
    result = TEST[x]
    print(result)
    x += 1

A list is created by putting the values between []. You access a particular element in the list by writing the name of the variable, followed by the index enclosed in []. Read more about lists here in the official tutorial.

Instead of the while loop with explicit indexing, it's nicer to use a for loop instead:

TEST = [10, 20, 30]

for element in TEST:
    result = element
    print(result)

answered Mar 27, 2020 at 9:02

Thomas

183k57 gold badges383 silver badges510 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Oksana Krasiuk Over a year ago

Thank you (that will solve my current issue), but is it any other way to do it, without using the list?

Thomas Over a year ago

There is, but it's fairly advanced and needlessly complex and error-prone. See the answer by @JosephChotard.

Joseph Chotard · Accepted Answer · 2020-03-27 09:09:36Z

2

I would recommend using a dictionary in most cases, however if you don't want to use a dictionary you can always use globals() or vars(). They work as follows:

global_var = 5
>> 5
print(globals()["global_var"])
>> 5

vars() works in the same way but at module scope.

In your case, do the following:

x = 0
y = 3

TEST0 = 10 
TEST1 = 20 
TEST2 = 30

while x < y:
    result = globals()['TEST{}'.format(x)]
    print(result)
    x += 1

answered Mar 27, 2020 at 9:09

Joseph Chotard

6855 silver badges15 bronze badges

1 Comment

Oksana Krasiuk Over a year ago

Thank you for the answer, (sorry do not have enough reputation to upvote). Have marked as an answer not your reply, to make sure that in the future other people will stick with a list (Sorry again)

Collectives™ on Stack Overflow

Python convert String to Variable in the loop

2 Answers 2

2 Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related