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The syntax of the Python programming language is the set of rules that defines how a Python program will be written and interpreted (by both the runtime system and by human readers). The Python language has many similarities to Perl , C , and Java .
Name resolution (including scope) varies between programming languages, and within a programming language, varies by type of entity; the rules for scope are called scope rules (or scoping rules). Together with namespaces , scope rules are crucial in modular programming , so a change in one part of the program does not break an unrelated part.
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.
In Python, if a name is intended to be "private", it is prefixed by one or two underscores. Private variables are enforced in Python only by convention. Names can also be suffixed with an underscore to prevent conflict with Python keywords. Prefixing with double underscores changes behaviour in classes with regard to name mangling.
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).
Instead, the name of the parent or base class is used followed by the scope resolution operator. For example, the following code presents two classes, the base class Rectangle, and the derived class Box. Box overrides the Rectangle class's Print method, so as also to print its height. [7]
Some languages allow variable shadowing in more cases than others. For example Kotlin allows an inner variable in a function to shadow a passed argument and a variable in an inner block to shadow another in an outer block, while Java does not allow these. Both languages allow a passed argument to a function/Method to shadow a Class Field.
Scope is an important part of the name resolution of a variable. Most languages define a specific scope for each variable (as well as any other named entity), which may differ within a given program. The scope of a variable is the portion of the program's text for which the variable's name has meaning and for which the variable is said to be ...