Reassining variables - oop

Question

I was doing a test project just to train my Python and I stumbled upon something that I don't quite understand so I would appreciate if someone explained it to me.
Below, I'm giving two similar Test scripts that give different results and I don't know why that is so:
class Test:
def __init__(self):
self.test = ""
self.testing("test_word", self.test)
def testing(self, word, test_var):
print(f"{self.test = }")
print(f"{test_var = }")
self.test = word
print(f"{self.test = }")
print(f"{test_var = }")
if __name__ == "__main__":
Test()
class Test1:
def __init__(self):
self.test = ["", ""]
self.testing("test_word", self.test)
def testing(self, word, test_var):
print(f"{self.test = }")
print(f"{test_var = }")
self.test[0] = word
print(f"{self.test = }")
print(f"{test_var = }")
if __name__ == "__main__":
Test1()
[What I DON'T understand]
Why in the case with the list (Test1), when I assign the first item in "self.test" to be "test_word", it also assigns it to the local, already passed list "test_var" as well, whereas in the other example (Test), when using a string variable I assign "self.test" to be "test_word" but the local "test_var" argument stays an empty string. I thought both these Test classes should give the same output, so why don't they?
P.S: I did a little more testing and found out that in the case with lists the test_var IS self.test, so they're pointing to the same object, whereas in the case of the string, in the beginning they have the same value but they're not referencing the same object. So in that case, how would I get a copy of the list instead of referencing the same object? Maybe I can assign a copy at the beginning of the "testing" method but is there a way to do it by passing arguments?
I'm sorry if this is a duplicate question, I couldn't find an answer to it.

Answer 1

I think I mostly answered my own question.
Here's a bunch of tests that you can copy-paste and execute to see the difference:
class Test:
def __init__(self):
self.test = ""
self.testing("test_word", self.test)
def testing(self, word, test_var):
print(f"{self.test = }")
print(f"{test_var = }")
self.test = word
print(f"{self.test = }")
print(f"{test_var = }")
print(test_var is self.test)
if __name__ == "__main__":
print("-"*50)
Test()
class Test0:
def __init__(self):
self.test = ""
self.testing("test_word")
def testing(self, word):
test_var = self.test
print(f"{self.test = }")
print(f"{test_var = }")
self.test = word
print(f"{self.test = }")
print(f"{test_var = }")
print(test_var is self.test)
if __name__ == "__main__":
print("-"*50)
Test0()
class Test1:
def __init__(self):
self.test = ["", ""]
self.testing("test_word", self.test)
def testing(self, word, test_var):
print(f"{self.test = }")
print(f"{test_var = }")
self.test[0] = word
print(f"{self.test = }")
print(f"{test_var = }")
print(test_var is self.test)
if __name__ == "__main__":
print("-"*50)
Test1()
class Test2:
def __init__(self):
self.test = ["", ""]
self.testing("test_word")
def testing(self, word):
test_var = self.test
print(f"{self.test = }")
print(f"{test_var = }")
self.test[0] = word
print(f"{self.test = }")
print(f"{test_var = }")
print(test_var is self.test)
if __name__ == "__main__":
print("-"*50)
Test2()
class Test3:
def __init__(self):
self.test = ["", ""]
self.testing("test_word")
def testing(self, word):
test_var = self.test.copy()
print(f"{self.test = }")
print(f"{test_var = }")
self.test[0] = word
print(f"{self.test = }")
print(f"{test_var = }")
print(test_var is self.test)
if __name__ == "__main__":
print("-"*50)
Test3()
class Test4:
def __init__(self):
self.test = ["", ""]
self.testing("test_word", self.test.copy())
def testing(self, word, test_var):
print(f"{self.test = }")
print(f"{test_var = }")
self.test[0] = word
print(f"{self.test = }")
print(f"{test_var = }")
print(test_var is self.test)
if __name__ == "__main__":
print("-"*50)
Test4()
Output:
--------------------------------------------------
self.test = ''
test_var = ''
self.test = 'test_word'
test_var = ''
False
--------------------------------------------------
self.test = ''
test_var = ''
self.test = 'test_word'
test_var = ''
False
--------------------------------------------------
self.test = ['', '']
test_var = ['', '']
self.test = ['test_word', '']
test_var = ['test_word', '']
True
--------------------------------------------------
self.test = ['', '']
test_var = ['', '']
self.test = ['test_word', '']
test_var = ['test_word', '']
True
--------------------------------------------------
self.test = ['', '']
test_var = ['', '']
self.test = ['test_word', '']
test_var = ['', '']
False
--------------------------------------------------
self.test = ['', '']
test_var = ['', '']
self.test = ['test_word', '']
test_var = ['', '']
False