In Python, it's both - the basic structured-programming advice to avoid global variables is always good, but it's a specific quirk of Python that makes global v

In Python, it's both - the basic structured-programming advice to avoid global variables is always good, but it's a specific quirk of Python that makes global variables (including built-in functions) slower than local variables. Python has full dynamic scoping, which means that inside a function you can refer to any variables set in outer scopes. Because Python is a dynamic language, every time you refer to a variable, the Python interpreter looks for it in the local scope first, and then each enclosing scope until it hits the containing module. A local variable will always be found in the first iteration of that loop, a global variable will take at least two iterations.