2. Introduction to Mapping Data Types in Python
Mapping data types in Python allow us to
store data in key-value pairs.
The most common mapping data type in
Python is the dictionary.
Mapping data types are mutable, meaning
their values can be changed.
3. Working with Dictionaries
Dictionaries are created using curly braces
{} or the dict() constructor.
Keys in a dictionary must be unique and
immutable, such as strings or numbers.
Values in a dictionary can be of any data
type and can be accessed using their
corresponding keys.
4. Basic Operations with Dictionaries
Accessing values in a dictionary is done by
using the key inside square brackets [].
We can add new key-value pairs to a
dictionary by assigning a value to a new
key.
To remove a key-value pair from a
dictionary, we can use the del keyword
followed by the key.
5. Common Methods for Dictionaries
The len() function returns the number of
key-value pairs in a dictionary.
The keys() method returns a list of all keys
in the dictionary.
The values() method returns a list of all
values in the dictionary.
6. Dictionary Comprehension
Dictionary comprehension allows us to
create dictionaries in a concise way.
We can use a loop to iterate over a
sequence and create key-value pairs.
It follows the format {key_expression:
value_expression for item in sequence}.
7. Other Mapping Data Types
Besides dictionaries, Python also provides
other mapping data types like OrderedDict
and Counter.
OrderedDict is a dictionary subclass that
remembers the order in which key-value
pairs were added.
Counter is a dictionary subclass that counts
the number of occurrences of each element
in a sequence.
8. Immutable Mapping Data Types
In addition to mutable mapping data types,
Python also offers immutable ones like
frozenset.
A frozenset is an immutable version of the
set data type and can be used as a key in a
dictionary.
Immutable mapping data types are useful
when we need to ensure that the keys
won't change.
9. Summary
Mapping data types in Python store data in
key-value pairs and are mutable.
Dictionaries are the most common mapping
data type and support various operations
and methods.
Other mapping data types like OrderedDict
and Counter provide additional
functionality.
10. References
Python Documentation: Mapping Types
dict. Available at:
https://docs.python.org/3/library/stdtypes.ht
ml#dict.
Python Documentation: Dictionary
Comprehension. Available at:
https://docs.python.org/3/tutorial/datastruct
ures.html#dictionaries.
