'Return' function doesn't return variable python

Question

Essentially, the variable 'exists' doesn't return. The output is "false, true, false," but I cannot see why it should be. As can be seen from the code, I have tried making the variable 'exists' global to no effect.

I've looked around and found two similar questions- Python--Function not returning value, Python: Return possibly not returning value, but cannot understand why my code doesn't work.

I'm aware that this question is very specific- if it's a silly mistake I've missed then I'll remove it, if it's a Python caveat then I'll see whether I can rephrase it.

import time
global exists
exists= False
def in_thread(exists):
 print(exists)
 time.sleep(2)
 exists= True
 print(exists)
 return(exists)
in_thread(exists)
print(exists)

• JrmDel: If you modify the value of a global variable, you need to call it at the beginning of your function. It might be a part of the problem

Answer 1

The exists inside of in_thread is a different variable from the exists outside. If you want to use the same variable, use the global keyword:

exists = False
def somefunction():
 global exists
 exists = True
print(exists)
someFunction()
print(exists)
# False
# True

Also, in_thread looks like it's not returning anything because you're not assigning the result to anything (you're just printing a local version of exists).

Answer 2

You really should consider rewriting your function to be as such:

import time
def in_thread():
 exists = False
 print(exists)
 time.sleep(2)
 exists = True
 return(exists)
print(in_thread())

It is returning, but it's returning its own version of exists when you declare exists outside the function. Instead consider creating it inside the function and call it in a print statement so it prints the output from the return.

This will lead to the output:

False
True

If you want to use your original function as written, you need to change your call to be in a print statement so you print the returned value:

import time
global exists
exists= False
def in_thread(exists):
 print(exists)
 time.sleep(2)
 exists= True
 print(exists)
 return(exists)
print(in_thread(exists))

Answer 3

print(exists) returns the global variable value which is set to False.

To print the value from you function, you would need to call the function inside of print() print(in-thread(exists))

Replace: in_thread(exists) print(exists)

With: print(in_thread(exists))