Python has a number of mapping collections. A mapping is an association between a key and a value. The built-in mapping collection is the dict
class. The other mappings are defined in the collections
library, and must be imported.
Items that are keys within a mapping must be immutable; they must provide a proper hash value as well as a matching equality test. The values within a mapping have no restrictions; they can be mutable or immutable. The order of the keys is not maintained by the dict
class.
We can create a simple dict
display using {}
; each key and value are separated by the :
character.
Here's an example of a simple mapping:
sieve = {2: True, 3: True, 4: False, 5: True, 6: None, 7: None}
We've created a simple mapping with keys that are all integers, and values which are a mixture of Boolean and None
values.
We can also create a dictionary using the dict()
function. This function can build a dictionary from a variety of sources. We can provide an existing dictionary as an argument...