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The input to eval is not necessarily a string; it may be structured representation of code, such as an abstract syntax tree (like Lisp forms), or of special type such as code (as in Python). The analog for a statement is exec , which executes a string (or code in other format) as if it were a statement; in some languages, such as Python, both ...
Introduced in Python 2.2 as an optional feature and finalized in version 2.3, generators are Python's mechanism for lazy evaluation of a function that would otherwise return a space-prohibitive or computationally intensive list. This is an example to lazily generate the prime numbers:
For example, in Python, to print the string Hello, World! followed by a newline, one only needs to write print ("Hello, World!" In contrast, the equivalent code in C++ [ 7 ] requires the import of the input/output (I/O) software library , the manual declaration of an entry point , and the explicit instruction that the output string should be ...
The phrase grammar of most programming languages can be specified using a Type-2 grammar, i.e., they are context-free grammars, [8] though the overall syntax is context-sensitive (due to variable declarations and nested scopes), hence Type-1. However, there are exceptions, and for some languages the phrase grammar is Type-0 (Turing-complete).
An input argument (the argument to an input parameter) must be a value, such as an initialized variable or literal, and must not be redefined or assigned to; an output argument must be an assignable variable, but it need not be initialized, any existing value is not accessible, and must be assigned a value; and an input/output argument must be ...
In Python, functions are first-class objects, just like strings, numbers, lists etc. This feature eliminates the need to write a function object in many cases. Any object with a __call__() method can be called using function-call syntax. An example is this accumulator class (based on Paul Graham's study on programming language syntax and ...
In many computer languages the keyword "input" is used as a special keyword or function, such as in Visual Basic or Python. The command "input" is used to give the machine the data it has to process. The command "input" is used to give the machine the data it has to process.
In object-oriented programming, a class defines the shared aspects of objects created from the class. The capabilities of a class differ between programming languages, but generally the shared aspects consist of state and behavior that are each either associated with a particular object or with all objects of that class. [1] [2]