Variable scope inside and outside functions - global statement being overridden by assignation unless preceded by reference

[Jacob Kruger]

Hi there


Working with python 3.11, and, issue that confused me for a little 
while, trying to figure out what was occurring - unless am completely 
confused, or missing something - was that, for example, when having 
pre-defined a variable, and then included it in the global statement 
inside a function, that function was still referring to a completely 
local instance, without manipulating outside variable object at all 
unless I first executed a form of referral to it, before then possibly 
assigning a new value to it.


Now, this does not seem to occur consistently if, for example, I just 
run bare-bones test code inside the python interpreter, but consistently 
occurs inside my actual testing script.


Basically, in a file with python code in that am using for a form of
testing at the moment, at the top of the file, under all the import
statements, I initiate the existence of a list variable to make use of

later:


# code snippet

l_servers = []

# end of first code snippet


Then, lower down, inside a couple of different functions, the first line
inside the functions includes the following:
# code snippet
     global l_servers
# end code snippet

That should, in theory, mean that if I assign a value to that variable
inside one of the functions, it should reflect globally?

However, it seems like that, while inside those functions, it can be
assigned a new list of values, but if I then return to the scope outside

the functions, it has reverted back to being an empty list = []?


The issue seems to specifically (or not) occur when I make a call to one 
function, and, in the steps it's executing in one context, while it's 
not doing anything to the list directly, it's then making a call to the 
second function, which is then meant to repopulate the list with a brand 
new set of values.


Now, what almost seems to be occurring, is that while just manipulating 
the contents of a referenced variable is fine in this context, the 
moment I try to reassign it, that's where the issue is occurring .


Here are relevant excerpts from the file:-


# start code

# original assignation in main part of file

l_servers = []


# function wich is initially being executed

def interact():
     global l_servers
     # extra code inbetween choosing what to carry out

     # ...

     # end of other code

     bl_response, o_out = list_servers()

     if bl_response: # just make sure other function call was successful

         l_servers.clear() # first make reference to global variable

         for srv in o_out: l_servers.append(srv) # now re-populate items

     # end code snippet from inside interact function

# end of interact function

# end of code snippet


That other function being called from within, list_servers() was 
initially just trying to populate the values inside the global list 
variable itself, but was ending up in a similar fashion - reverting to 
initial empty value, but, the above now seems to work, as long as I 
first make reference to/manipulate/work with global variable instead of 
just trying to reassign it a brand new value/set of items?


So, am I missing something obvious, have I forgotten about something 
else - yes, know that if was working from within an embedded function, I 
might need/want to then use the nonlocal statement against that variable 
name, but, honestly, just not sure how this can be occurring, and, it's 
not just with this one list variable, etc.?


If I try simple test code from within the python interpreter, using 
different types of variables, this does also not seem to be the same all 
the time, but, don't think it can relate to an iterable like a list, or 
else, just in case, here is the code snippet with all the import 
statements from the top of that file, in case something could be 
overriding standard behaviour - not likely in this context, but, really 
not sure what's occurring:

# import code snippet

import requests, time
from requests.auth import HTTPBasicAuth
import psutil as psu
import pytz
import bcrypt
from copy import copy
from datetime import datetime, timedelta, timezone
from dateutil.parser import parse

# end of import snippet


Thanks if you have any ideas/thoughts on the matter


Jacob Kruger
+2782 413 4791
"Resistance is futile!...Acceptance is versatile..."