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Python sets are very much like mathematical sets, and support operations like set intersection and union. Python also features a frozenset class for immutable sets, see Collection types. Dictionaries (class dict) are mutable mappings tying keys and corresponding values. Python has special syntax to create dictionaries ({key: value})
Parse tree of Python code with inset tokenization. The syntax of textual programming languages is usually defined using a combination of regular expressions (for lexical structure) and Backus–Naur form (a metalanguage for grammatical structure) to inductively specify syntactic categories (nonterminal) and terminal symbols. [7]
Other examples include interpreter directives: The Unix "shebang" – #! – used on the first line of a script to point to the interpreter to be used. "Magic comments" identifying the encoding a source file is using, [21] e.g. Python's PEP 263. [22] The script below for a Unix-like system shows both of these uses:
In computer programming, specifically when using the imperative programming paradigm, an assertion is a predicate (a Boolean-valued function over the state space, usually expressed as a logical proposition using the variables of a program) connected to a point in the program, that always should evaluate to true at that point in code execution.
Programming languages can have multiple implementations. Different implementations can be written in different languages and can use different methods to compile or interpret code. For example, implementations of Python include: [9] CPython, the reference implementation of Python; IronPython, an implementation targeting the .NET Framework ...
While high-level languages such as Python or Haskell use unbounded integers by default, lower-level programming languages such as C or assembly language typically operate on finitely-sized machine words, which are more suitably modeled using the integers modulo (where n is the bit width of a machine word). There are several abstract domains ...
A built-in function, or builtin function, or intrinsic function, is a function for which the compiler generates code at compile time or provides in a way other than for other functions. [23] A built-in function does not need to be defined like other functions since it is built in to the programming language. [24]
In computer science, an interpreter is a computer program that directly executes instructions written in a programming or scripting language, without requiring them previously to have been compiled into a machine language program. An interpreter generally uses one of the following strategies for program execution: