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Variable scope in Python is implicitly determined by the scope in which one assigns a value to the variable, unless scope is explicitly declared with global or nonlocal. [22] Note that the closure's binding of a name to some value is not mutable from within the function. Given: >>>
In computer programming, variable shadowing occurs when a variable declared within a certain scope (decision block, method, or inner class) has the same name as a variable declared in an outer scope. At the level of identifiers (names, rather than variables), this is known as name masking .
For variables, Python has function scope, module scope, and global scope. Names enter context at the start of a scope (function, module, or global scope), and exit context when a non-nested function is called or the scope ends. If a name is used prior to variable initialization, this raises a runtime exception.
The term closure is often used as a synonym for anonymous function, though strictly, an anonymous function is a function literal without a name, while a closure is an instance of a function, a value, whose non-local variables have been bound either to values or to storage locations (depending on the language; see the lexical environment section below).
The scope of a variable describes where in a program's text the variable may be used, while the extent (also called lifetime) of a variable describes when in a program's execution the variable has a (meaningful) value. The scope of a variable affects its extent. The scope of a variable is actually a property of the name of the variable, and the ...
In computer programming, a static variable is a variable that has been allocated "statically", meaning that its lifetime (or "extent") is the entire run of the program. This is in contrast to shorter-lived automatic variables, whose storage is stack allocated and deallocated on the call stack; and in contrast to dynamically allocated objects, whose storage is allocated and deallocated in heap ...
An identifier I' (for variable X') masks an identifier I (for variable X) when two conditions are met I' has the same name as I; I' is defined in a scope which is a subset of the scope of I; The outer variable X is said to be shadowed by the inner variable X'. For example, the parameter "foo" shadows the local variable "foo" in this common pattern:
In many languages, the scope resolution operator is written ::. In some languages, notably those influenced by Modula-3 (including Python and Go), modules are objects, and scope resolution within modules is a special case of usual object member access, so the usual method operator . is used for scope resolution.