Python Language List: Difference between revisions
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empty_list = list() | empty_list = list() | ||
</syntaxhighlight> | </syntaxhighlight> | ||
The <code>list()</code> function converts the data types to lists. The data types that can be converted are: | |||
* Strings | |||
* Tuples | |||
=Access a List= | =Access a List= |
Revision as of 23:50, 6 March 2022
Internal
Overview
A list is a mutable sequence type that contains zero or more elements and whose elements can be of the same type or different types. The elements of a list are ordered. As mentioned, the list is mutable, in that a list can be changed in-place, new elements can be added to it, and existing elements can be overwritten. Unlike a set, a list can contain the same element multiple times, a list element does not need to be unique in the list.
List type()
The function type()
applied to a list returns:
<class 'list'>
To check whether an instance is a list:
i = ...
if type(i) is list:
...
For list
subclasses:
i = ...
if isinstance(i, list):
...
Create a List
A list can be created with the []
syntax, with the list()
functions and with list comprehensions.
Create a List with []
A list can be created specifying the list elements, separate them by comma and enclose them in square brackets.
empty_list = []
some_list = ['A', 'B', 'C']
some_other_list = ['A', 2, 3.0, ['B', 4]]
Create a List or Convert other Data Type to a List with list()
An empty list can be created with the list()
function:
empty_list = list()
The list()
function converts the data types to lists. The data types that can be converted are:
- Strings
- Tuples
Access a List
Test for Empty List
Test for Existence of an Element in List
Size of a List
The number of elements is given by the len()
function:
l = [...]
print(len(l))
Iterate over a List
l = ['A', 'B', 'C']
for i, e in enumerate(l):
print(f'index: {i}, element: {e}')
Slices
Assign the sublist to l
:
l = l[:-1]
Modify a List
Modify Individual Elements
Append an Element
l.append(e)
Delete the Last Element
del l[-1]
Delete All Elements
List Processing
split(), join()
Sorting
TO DEPLETE
Join the List Elements in a String
Join the elements of the given list in a string, using '-' as separator:
li = ['a', 'b']
s = '-'.join(li)
Only works if the list elements are strings.
Extract Elements from the Tail of the List Starting with a Certain Index
l = [1, 2, 3]
print(l[0:]) # prints [1, 2, 3]
print(l[1:]) # prints [2, 3]
print(l[2:]) # prints [3]
print(l[3:]) # prints [] (empty list)
print(l[4:]) # prints [] (empty list)
Extract Elements from the Head of the List Counting from the Tail
TODO