Previously. Pointers employed in Python, they are just hidden.
#!/usr/bin/env python3 def f(x): x.append(123) foo= f(foo) f(foo) print (foo)
What you see here is called call by reference (rather than by value). A pointer is passed rather than a whole list. You can use dictionary or set instead. It's like to pass a pointer to an object in pure C or C++.
This is useful when you have a function that add some data to a global list.
#!/usr/bin/env python3 def f(): lst= lst.append(123) lst.append(456) return lst foo= foo=foo+f() foo=foo+f() print (foo)
#!/usr/bin/env python3 def f(out): out.append(123) out.append(456) foo= f(foo) f(foo) print (foo)
In the second example, f() adds data directly to a list, pointer to which was passed. No need for additional list copying.
This can create a problem, however: f() can garble the list in a way that will be slightly harder to debug.
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