Python Collections (Arrays)
There are four collection data types in the Python programming language:
- List is a collection which is ordered and changeable. Allows duplicate members.
- Tuple is a collection which is ordered and unchangeable. Allows duplicate members.
- Set is a collection which is unordered and unindexed. No duplicate members.
- Dictionary is a collection which is unordered, changeable and indexed. No duplicate members.
When choosing a collection type, it is useful to understand the properties of that type. Choosing the right type for a particular data set could mean retention of meaning, and, it could mean an increase in efficiency or security.
A list is a collection which is ordered and changeable. In Python lists are written with square brackets.
Create a List:
Change the second item:
thislist = "blackcurrant"
The list() Constructor
It is also possible to use the list() constructor to make a list. To add an item to the list use append() object method. To remove a specific item use the remove() object method. The len() function returns the length of the list.
Using the list() constructor to make a List:
Using the append() method to append an item:
Using the remove() method to remove an item:
The len() method returns the number of items in a list:
Python has a set of built-in methods that you can use on lists.
|append()||Adds an element at the end of the list|
|clear()||Removes all the elements from the list|
|copy()||Returns a copy of the list|
|count()||Returns the number of elements with the specified value|
|extend()||Add the elements of a list (or any iterable), to the end of the current list|
|index()||Returns the index of the first element with the specified value|
|insert()||Adds an element at the specified position|
|pop()||Removes the element at the specified position|
|remove()||Removes the first item with the specified value|
|reverse()||Reverses the order of the list|
|sort()||Sorts the list|