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In computer science, an associative array, map, symbol table, or dictionary is an abstract data type that stores a collection of (key, value) pairs, such that each possible key appears at most once in the collection. In mathematical terms, an associative array is a function with finite domain. [ 1] It supports 'lookup', 'remove', and 'insert ...
the Add method, which adds a key and value and throws an exception if the key already exists in the dictionary; assigning to the indexer, which overwrites any existing value, if present; and assigning to the backing property of the indexer, for which the indexer is syntactic sugar (not applicable to C#, see F# or VB.NET examples).
Space. Θ ( n) [ 1] O ( n) A small phone book as a hash table. In computing, a hash table is a data structure often used to implement the map (a.k.a. dictionary or associative array) abstract data type. A hash table uses a hash function to compute an index, also called a hash code, into an array of buckets or slots, from which the desired value ...
Python syntax and semantics. A snippet of Python code with keywords highlighted in bold yellow font. 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 ...
List comprehension. A list comprehension is a syntactic construct available in some programming languages for creating a list based on existing lists. It follows the form of the mathematical set-builder notation ( set comprehension) as distinct from the use of map and filter functions.
Pandas' syntax for mapping index values to relevant data is the same syntax Python uses to map dictionary keys to values. For example, if s is a Series, s['a'] will return the data point at index a. Unlike dictionary keys, index values are not guaranteed to be unique.
In mathematics, the lexicographic or lexicographical order (also known as lexical order, or dictionary order) is a generalization of the alphabetical order of the dictionaries to sequences of ordered symbols or, more generally, of elements of a totally ordered set . There are several variants and generalizations of the lexicographical ordering.
Autovivification. In the Perl programming language, autovivification is the automatic creation of new arrays and hashes as required every time an undefined value is dereferenced. Perl autovivification allows a programmer to refer to a structured variable, and arbitrary sub-elements of that structured variable, without expressly declaring the ...