Python Lists

Python lists are containers to store a set of values of any data type. In lists, values are in a comma-separated way between square brackets. Values can be of any data type such as either containing a single data type like string, int only, or mixed types like string, int, boolean, etc. together.

Lists containing the same data types

Lists containing different data types

Here, in the above example, list2 contains different data types like numbers(int, float), string, boolean, and lists. You can also check the data type of values inside list2 as:

list2 = ['PythonSansar', 2022, 2.34, True, [1, 3, 5]]

# loop through list2
for value in list2:
   print(f'Value: {value} data type -> {type(value)}')

Output:

Value: PythonSansar data type -> <class 'str'>
Value: 2022 data type -> <class 'int'>
Value: 2.34 data type -> <class 'float'>
Value: True data type -> <class 'bool'>
Value: [1, 3, 5] data type -> <class 'list'>

Creating List

Python list can be created by two methods:

1. By list constructor: list( )

>>> list3 = list()
>>> type(list3)
<class 'list'>
>>> list3 = list(("List", "Set", "Dictionary", "Tuple"))
>>> list3
['List', 'Set', 'Dictionary', 'Tuple']
>>>

Note: Make sure to place list items inside parenthesis inside list constructor.

2. By simply placing square brackets: [ ]

>>> list4 = []
>>> type(list4)
<class 'list'>
>>> list4 = ["Learn", "Python", "Lists"]
>>> list4
['Learn', 'Python', 'Lists']
>>>

Indexing List

Python list can be indexed just like a string starting with the first index value 0 and so on. 

In string, each character is indexed with a certain value starting from 0, and we can access those characters by passing its index value.

Let’s take a simple example with “PythonSansar” as a string.

>>> string1 = "PythonSansar"
>>> #get first character
>>> string1[0]
'P'
>>> #get last character
>>> string1[-1]
'r'
>>>

Let’s try the same with the list items as:

list5 = [“Mark”, “Elon”, “Jeff”, “Bill”]

>>> list5 = ["Mark", "Elon", "Jeff", "Bill"]
>>> list5[0]
'Mark'
>>> list5[1]
'Elon'
>>> list5[3]
'Bill'
>>> list5[5]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
IndexError: list index out of range
>>>

Note: Since we have four items on the list5 we can access items from index range 0 to 4. Any other value pass different from index ranges results in “IndexError”.

Python Built-in functions on list

List support different python built-in functions like len( ), max( ), min( ), sum( ), and many others.

list6 = [10, 20, 30, 40, 50]

Length of the list: len( )

>>> len(list6)
5

Maximum item on the list: max( )

>>> max(list6)
50

Minimum item on the list: min()

>>> min(list6)
10

Sum of the list items: sum( )

>>> sum(list6)
150
>>>

Check out more on list: Python List Methods