Why am I able to access the class variable of type list and change its contents but not of type stri-CodePudding

I have below code:

class Employee:
    orgName = 'Credit Cards'  # class variable

    def __init__(self, name):
        self.name = name  # instance variable

Sam = Employee('Sam')
print(Sam.orgName) # 'Credit Cards'
Sam.orgName = 'Loans'
print(Sam.orgName) # 'Loans'
print(Employee.orgName) # 'Credit Cards'

So in the above example I understand that when I assign something to Sam.orgName. Python is actually creating an instance variable called 'orgName' and thus the class variable 'orgName' remains unchanged.

But then I tried below code here is where I am confused:

class Employee:
   orgName = 'Credit Cards'  # class variable
   hobbies = ['Hiking']

   def __init__(self, name):
      self.name = name  # instance variable

Sam = Employee('Sam')
print(Sam.hobbies) # 'Hiking'
Sam.hobbies.append('Reading')
print(Sam.hobbies) # 'Hiking', 'Reading'
print(Employee.hobbies) # 'Hiking', 'Reading'

How is it that I am able to modify the class variable here when it should follow the behavior of the first code snippet where Sam.hobbies should have created a list instance variable?

CodePudding user response：

There is a difference between how you modified the string member vs the list member. Initially the Employee static member is shared by the instance Sam (when Sam is initiated, it references whatever Employee references).

In the list case, you modified this list in-place, which altered the list for both because they point to the same object. In the string case, you changed the assignment of the variable for the Sam, so that this instance's version of orgName no longer points to the same thing as the Employee class does. Note that strings are immutable in python, so you could not have done an in-place modification in the same way anyway.