1

I have 2 files:

Main.py

from test import test
def main():
    sol = 'hello'
    if test() == sol:
        print('Yes')
    else:
        print('No')

test.py

def test():
    return 'hello'

Is there a way to access the sol variable in my test function which is in another file? I'd like to do something like this:

def test():
    return sol

This way it's always the same as the variable in Main.py. I tried a solution which is mentioned on Python extract variables from an imported file but it didn't work for me. Thank you for any help

Edit: I'd like to do it without changing the Main.py file

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6
  • Then, your output will always be Yes, what's the meaning of your code? Commented Sep 29, 2018 at 3:15
  • @lagom It's just a simple code to show my issue and what i'd like to do. I am curious if something like this is possible Commented Sep 29, 2018 at 3:17
  • Pass the variable to the function as a parameter? def test(sol): return sol Commented Sep 29, 2018 at 3:20
  • @TyloBedo would it be possible without changing the Main.py ? Commented Sep 29, 2018 at 3:21
  • You would need to pass the variable to test in Main.py if test(sol) == sol:. What are you actually trying to accomplish? I think you’re probably going about it in the wrong way. Commented Sep 29, 2018 at 3:25

3 Answers 3

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2

Since sol isn't defined in the function you will need to declare it as a global function so it can be used in the function. Change test.pyto the following...

test():
    global sol
    return sol

Hope that helps.

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1 Comment

I am very sorry, i forgot to mention the sol variable is in a function too. Would it be possible to access it like this?
2

If sol is a constant (i.e. a variable which will not change during the course of the program), then you can put it into a separate file, say var.py, and import it into both main.py and test.py:

from var import sol

BUT what you will be importing is a copy of the variable with the value it had at the time it was imported - any subsequent reassignments will not update the value of sol in test.py and main.py. Because a string is immutable, when you reassign a value to it what you are actually doing is you are reusing the variable name for a new entity.

What you need to do is have your variable in a mutable structure, such as a list or a class, so your var.py will look like this:

class v(object):
    sol = 'Hello'

and then in main.py and test.py you can refer to sol using:

from var import v
print(v.sol)

This way, any changes to v.sol will be correctly reflected anywhere class v is imported. A bit cumbersome, but that's how it is in Python.

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2 Comments

So there isn't really a way to do it without touching the main.py and creating a new file?
The cleanest way would be to put the shared variable in a separate file, which can be imported by all files which need access to the variable (via a mutable structure such as a class, list etc.) If you do not want to do that, you can put the class v in test.py, and then import it in main.py together with your test function.
1

You can use inspect module to get the sol variable from main function without change anything of main.py. Of course, you need to call main function.

Main.py:

from test import test
def main():
    sol = 'hello'
    if test() == sol:
        print('Yes')
    else:
        print('No')

main()

test.py:

import inspect

def test():
    frame = inspect.currentframe()
    sol_from_main = 'default'
    try:
        sol_from_main = frame.f_back.f_locals['sol'] # line A
    except:
        print('No sol found')
    print(sol_from_main)  # this print 'hello'
    return sol_from_main

Output:

hello

Yes

Explanation:

From the python doc, we can see next:

frame

f_back | next outer frame object (this frame’s caller)

f_locals | local namespace seen by this frame

So line A get the caller of current function, that is main function, and use f_locals to get all local variables of main function, so it can get the sol value from main. FYI in case you still need it.

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