Comparison of programming languages (associative array): Difference between revisions

Revision as of 21:56, 31 July 2020

Revision as of 22:04, 31 July 2020

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Some versions of [[Prolog]] include dictionary ("dict") utilities.<ref>[http://www.swi-prolog.org/pldoc/man?section=dicts "Dicts: structures with named arguments"]</ref>

=== [[Python (programming language)|Python]] ===

In [[Python]], associative arrays are called ''"[[Python syntax and semantics#Collection types|dictionaries]]''". Dictionary literals are markeddelimited withby curly braces:

<syntaxhighlight lang=Python>

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</syntaxhighlight>

To access an entry in Python simply use the array indexing operator. For example,:

<syntaxhighlight lang=Pycon>

>>> phonebook['Sally Smart']

'555-9999'

</syntaxhighlight>

An example loopLoop [[iterator#Python|iterating]] through all the keys of the dictionary:

<syntaxhighlight lang=Pycon>

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</syntaxhighlight>

Dictionary keys can be individually deleted using the <code>del</code> statement. The corresponding value can be returned before the key-value pair areis deleted using the "pop" method of "dict" typestype:

<syntaxhighlight lang=Pycon>

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</syntaxhighlight>

Python 2.7 and 3.x also supportssupport dictionary comprehensions[[list comprehension]], a compact syntax for generating a dictionary from any iterator:

<syntaxhighlight lang=Pycon>

>>> square_dict = {i: i*i for i in range(5)}

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</syntaxhighlight>

Strictly speaking, a dictionary is a super-set of an associative array, since neither the keys or values are limited to a single datatype. One could think of a dictionary as an ''"associative list''" using the nomenclature of Python. For example, the following is also legitimate:

<syntaxhighlight lang=Python>