Understanding Variable Passing in Python and Java

Python and Java don't pass variables the way you think they do. You think you're

handing a function your original variable, but it's not true call-by-reference. It’s called "call

by sharing." Imagine giving a friend a copy of your house address. They can go to your

house and mess with the furniture inside; that’s like modifying a list, and you'll see those

changes. But if your friend just tears up that copied address and writes down a new

one, it doesn't change your original address at all. That’s like reassigning

the variable inside the function. Your original variable is safe.