[Tutor] collections and mappings

[Steven D'Aprano]

On Fri, Jun 21, 2019 at 10:01:43AM +1000, mhysnm1964 at gmail.com wrote:

> I have reviewed the collection module and do not understand mappings. I have
> seen this in other languages and have never got the concept. Can someone
> explain this at a very high level.  

It might help if you remember that dicts are a kind of mapping.

Another name for dicts are "associative arrays".

In the most general terms, a mapping is an association between one or 
more pieces of information and another one or more pieces of 
information. That is so general as to be completely abstract, and I 
think it will be more useful to give some concrete examples.

If you are American, you probably have a social security number. There 
is a mapping between your social security number and you, the person: 
the government associates data about you with the social security 
number.

If you have used a regular paper dictionary, it is a mapping between 
words and definitions. We say the word maps to the definition.

In Python terms, we would use a dict, using the word as the key and the 
definition as the value. For example:

{"Childhood": 
        """"The period of human life intermediate between the idiocy 
        of infancy and the folly of youth—two removes from the sin of 
        manhood and three from the remorse of age.""",

 "Debt":
        """An ingenious substitute for the chain and whip of the 
        slave-driver.""",

 "Piano":
        """A parlor utensil for subduing the impenitent visitor. It 
        is operated by depressing the keys of the machine and the 
        spirits of the audience.""",

 "Quotation":
        """The act of repeating erroneously the words of another. 
        The words erroneously repeated."""
}




Does this help?




-- 
Steven