Set an external variable from another Python script

Question

I am going to try to be clear. I have a ex.py file I want to import in other py files. In the ex.py file there is a variable that I declare. However, I would like to declare that variable in the other py files.

I have a file ex.py:

variable = 5
whatever = 10 + variable

For example in an other .py file, I would have:

from ex import whatever
variable = 10
print(whatever)  # whatever object uses the variable

The result from printing whatever will be 15. I would like to have 20 as i declare variable in the new script.

That is to streamline the code so that the same .py file can be used in several other files. Any contribution please.

What would be the contents of ex.py and what is the expected output of print(whatever)? — metatoaster
– metatoaster, Commented Jan 16, 2020 at 2:24
Your code looks fine, as far as it goes. What's the problem? — martineau
– martineau, Commented Jan 16, 2020 at 2:26

Taxel · Accepted Answer · 2020-01-16 02:43:36Z

2

If I understand you correctly, you want whatever to always be variable + 5, right? If you set whatever in the ex.py, its value is fixed to 15 and will not change. In this case you should declare a function which calculates whatever dynamically, like so:

def whatever(variable):
  return variable + 5

If you want to have multiple .py files accessing the same global variable (the other interpretation of your question I can come up with), you might want to have a look at the singleton pattern

answered Jan 16, 2020 at 2:43

Taxel

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2 Comments

delalma Over a year ago

your comment is very useful. however, i am not sure it is the correct answer. I want whatever to always be variable + 10 in that case. variable from the new .py file + 10 from the ex.py file.

Barmar Over a year ago

@delalma It's not possible to make a variable change automatically like that. There's no way to link variables. If you want something to calculate dynamically, you need a function.

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