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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})
In PHP and R, all arrays can be associative, except that the keys are limited to integers and strings. In JavaScript (see also JSON), all objects behave as associative arrays with string-valued keys, while the Map and WeakMap types take arbitrary objects as keys. In Lua, they are used as the primitive building block for all data structures.
Stability is also not an issue if all keys are different. Unstable sorting algorithms can be specially implemented to be stable. One way of doing this is to artificially extend the key comparison so that comparisons between two objects with otherwise equal keys are decided using the order of the entries in the original input list as a tie-breaker.
As in Perl 5, Perl 6 default hashes are flat: keys are strings and values are scalars. One can define a hash to not coerce all keys to strings automatically: these are referred to as "object hashes", because the keys of such hashes remain the original object rather than a stringification thereof.
Lexicographic sorting of a set of string keys can be implemented by building a trie for the given keys and traversing the tree in pre-order fashion; [26] this is also a form of radix sort. [27] Tries are also fundamental data structures for burstsort , which is notable for being the fastest string sorting algorithm as of 2007, [ 28 ...
Python uses the + operator for string concatenation. Python uses the * operator for duplicating a string a specified number of times. The @ infix operator is intended to be used by libraries such as NumPy for matrix multiplication. [104] [105] The syntax :=, called the "walrus operator", was introduced in Python 3.8. It assigns values to ...
There are plenty of reason you might feel off in the late afternoon and evening. Maybe you’re mentally wiped after socializing all day, or your brain is fried from hours of work.
Such a component or property is called a sort key. For example, the items are books, the sort key is the title, subject or author, and the order is alphabetical. A new sort key can be created from two or more sort keys by lexicographical order. The first is then called the primary sort key, the second the secondary sort key, etc.