It is an example of slice notation, and what it does depends on the type of population. If population is a list, this line will create a shallow copy of the list. For an object of type tuple or a str, it will do nothing (the line will do the same without [:]), and for a (say) NumPy array, it will create a new view to the same data.
W3Schools
w3schools.com › python › python_lists.asp
Python Lists
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, unchangeable*, and unindexed.
Python documentation
docs.python.org › 3 › tutorial › datastructures.html
5. Data Structures — Python 3.14.6 documentation
We saw that lists and strings have many common properties, such as indexing and slicing operations. They are two examples of sequence data types (see Sequence Types — list, tuple, range). Since Python is an evolving language, other sequence data types may be added.
python - What does [:] mean? - Stack Overflow
I'm analyzing some Python code and I don't know what pop = population[:] means. Is it something like array lists in Java or like a bi-dimensional array? More on stackoverflow.com
python - What's the difference between [] and {} vs list() and dict()? - Stack Overflow
I understand that they are both essentially the same thing. But in terms of creating an empty list or dict, are there any differences? More on stackoverflow.com
How "list" is implemented in Python?
Basically the list is implemented in the python virtual machine that runs the python code. It's written in C and here is the source code: https://github.com/python/cpython/blob/main/Objects/listobject.c If you are unfamiliar with C, that is basically like and ArrayList or a "dynamic array". It's a list that is a backed by an array. Array is a continuous memory segment that can be used to store stuff. There are really no directly accessible arrays in python by design. Arrays are fixed size, so the "dynamic array" refers to the fact that the insert/add/remove functions guarantee that the array is replaced with a new, longer array when it becomes full. More on reddit.com
25
45
August 26, 2024Python list
Sure. A list is a data type, what is does is stores other types of data in order example = [I’m a string”, 2, 2.45, [“i’am”, “a” “list inside”, “another”], (“tuples”, 2,3), {“set”}, {“my” : “dictionary”}] Types are important to Python, a list is really important to Python because it’s ordered. Each list can be indexed and sliced because they are ordered. print(example[2]) >>>2.45 List start their index at 0 so [2] is the third element. But the last item is… print(example[-1]) >>>{“my”, “dictionary} We can slice them further. print(example[1:4]) #print 2nd to 5th element. >> [2, 2.45, [“i’am”, “a” “list inside”, “another”]] Slicing format example[start:stop:step] and we can go further if we know it’s list and lists, print(example[4][2]) >>>”list inside” Step will skip x amount hint in the list i.e. every 4th element. This can be done negatively as well. And reverse the list. We can loop directly through list… for element in example: if element == 2: break print(“No 2 in the list”) Or check with in if 2 in example: print(“There is a 2”) List can have comprehensions, we loved them so much we made them easier to make list_of_squares = [number**2 for number in range(5)] Lists are great because like all types they have useful methods. Such as, sort(), .append(), .insert(). You can easy check how many elements there are with len(). And since lists in Python can hold anything, anything, you can do a lot of complex requests coming from them. Lists are great for…loops. We want to do the same thing to a bunch of other things. More on reddit.com
3
2
August 21, 2023Videos
14:40
Lists in Python Explained Simply (Full Tutorial) - YouTube
06:34
Python lists 🧾 - YouTube
15:52
The Most Complete Tutorial on Python Lists - YouTube
19:40
Lists in Python EXPLAINED | Python Lists | Python Tutorial for ...
11:36
Python Lists Explained: Tips, Tricks, and Techniques You Need to Know!
Google
developers.google.com › google for education › python › python lists
Python Lists | Python Education | Google for Developers
Python's built-in list type is defined using square brackets [ ] and elements are accessed using zero-based indexing.
GeeksforGeeks
geeksforgeeks.org › python › python-lists
Python Lists - GeeksforGeeks
List is a built-in data structure used to store an ordered collection of items.
Published June 16, 2026
Purple Frog Systems
purplefrogsystems.com › home › python lists – what do i need to know?
Python Lists – What do I need to know? - Purple Frog Systems
July 22, 2025 - In this post, we’ll cover everything you need to know about Python lists: what they are, how they work, and how to use them efficiently. What is a Python List? A list is a mutable, ordered, heterogeneous collection of items.
Stanford CS
cs.stanford.edu › people › nick › py › python-list.html
Python Lists
However, list-specific functions like append() and remove() do not work on iterables. If you have an iterable and need a list, it's easy to construct a list from the iterable like this: ... Why do Python functions return an iterable instead of a full list? Because the iterable is more lightweight and efficient compared to a list.
W3Schools
w3schools.com › python › ref_func_list.asp
Python list() Function
Read more about list in the chapter: Python Lists.
Codecademy
codecademy.com › learn › introduction-to-python-for-finance › modules › learn-python3-lists › cheatsheet
Introduction to Python: Lists Cheatsheet | Codecademy
In order to add one item, create a new list with a single value and then use the plus symbol to add the list. ... In Python, lists are a versatile data type that can contain multiple different data types within the same square brackets.
Top answer 1 of 6
137
It is an example of slice notation, and what it does depends on the type of population. If population is a list, this line will create a shallow copy of the list. For an object of type tuple or a str, it will do nothing (the line will do the same without [:]), and for a (say) NumPy array, it will create a new view to the same data.
2 of 6
38
It might also help to know that a list slice in general makes a copy of part of the list. E.g. population[2:4] will return a list containing population[2] and population[3] (slicing is right-exclusive). Leaving away the left and right index, as in population[:] they default to 0 and length(population) respectively, thereby selecting the entire list. Hence this is a common idiom to make a copy of a list.
Top answer 1 of 11
248
In terms of speed, it's no competition for empty lists/dicts:
>>> from timeit import timeit
>>> timeit("[]")
0.040084982867934334
>>> timeit("list()")
0.17704233359267718
>>> timeit("{}")
0.033620194745424214
>>> timeit("dict()")
0.1821558326547077
and for non-empty:
>>> timeit("[1,2,3]")
0.24316302770330367
>>> timeit("list((1,2,3))")
0.44744206316727286
>>> timeit("list(foo)", setup="foo=(1,2,3)")
0.446036018543964
>>> timeit("{'a':1, 'b':2, 'c':3}")
0.20868602015059423
>>> timeit("dict(a=1, b=2, c=3)")
0.47635635255323905
>>> timeit("dict(bar)", setup="bar=[('a', 1), ('b', 2), ('c', 3)]")
0.9028228448029267
Also, using the bracket notation lets you use list and dictionary comprehensions, which may be reason enough.
2 of 11
57
In my opinion [] and {} are the most pythonic and readable ways to create empty lists/dicts.
Be wary of set()'s though, for example:
this_set = {5}
some_other_set = {}
Can be confusing. The first creates a set with one element, the second creates an empty dict and not a set.
Reddit
reddit.com › r/learnpython › how "list" is implemented in python?
r/learnpython on Reddit: How "list" is implemented in Python?
August 26, 2024 -
Lately finding myself looking around in builtins.py file trying to learn/understand how the language works. Today I was reading about lists and how they work and etc. And as usually I end up in a class list in builtins.py file. I am now surprised that all the functions of list class is empty. For example, method append has 'pass' in it. And that is it.
Here is a code:
class list(object):
"""
Built-in mutable sequence.
If no argument is given, the constructor creates a new empty list.
The argument must be an iterable if specified.
"""
def append(self, *args, **kwargs): # real signature unknown
""" Append object to the end of the list. """
pass
def clear(self, *args, **kwargs): # real signature unknown
""" Remove all items from list. """
pass
def copy(self, *args, **kwargs): # real signature unknown
""" Return a shallow copy of the list. """
passI wonder how this works? Why all methods are empty?
Top answer 1 of 6
50
Basically the list is implemented in the python virtual machine that runs the python code. It's written in C and here is the source code: https://github.com/python/cpython/blob/main/Objects/listobject.c If you are unfamiliar with C, that is basically like and ArrayList or a "dynamic array". It's a list that is a backed by an array. Array is a continuous memory segment that can be used to store stuff. There are really no directly accessible arrays in python by design. Arrays are fixed size, so the "dynamic array" refers to the fact that the insert/add/remove functions guarantee that the array is replaced with a new, longer array when it becomes full.
2 of 6
4
Here's a breakdown of the C source code that you might find helpful: http://www.laurentluce.com/posts/python-list-implementation/ Other stack overflow answers to this will help too: https://stackoverflow.com/questions/3917574/how-is-pythons-list-implemented
Programiz
programiz.com › python-programming › list
Python List (With Examples)
December 30, 2025 - In Python, lists allow us to store multiple items in a single variable.
Data Science Discovery
discovery.cs.illinois.edu › learn › Basics-of-Data-Science-with-Python › Lists-and-Functions-in-Python
Lists and Functions in Python - Data Science Discovery
A list is a built-in data structure in Python, meaning we do not need to import any libraries to use it, and is used to store a collection of items (in order).
Real Python
realpython.com › python-list
Python's list Data Type: A Deep Dive With Examples – Real Python
October 21, 2023 - Lists are sequences of objects. They’re commonly called containers or collections because a single list can contain or collect an arbitrary number of other objects. Note: In Python, lists support a rich set of operations that are common to ...
YouTube
youtube.com › cs dojo
Introduction To Lists In Python (Python Tutorial #4) - YouTube
How to use Python lists. This entire series in a playlist: https://goo.gl/eVauVX Keep in touch on Facebook: https://www.facebook.com/entercsdojo Download the...
Published January 12, 2018 Views 684K
Reddit
reddit.com › r/learnpython › python list
r/learnpython on Reddit: Python list
August 21, 2023 -
Can someone give me a break down on python lists I'm not understanding
Top answer 1 of 3
6
Sure. A list is a data type, what is does is stores other types of data in order example = [I’m a string”, 2, 2.45, [“i’am”, “a” “list inside”, “another”], (“tuples”, 2,3), {“set”}, {“my” : “dictionary”}] Types are important to Python, a list is really important to Python because it’s ordered. Each list can be indexed and sliced because they are ordered. print(example[2]) >>>2.45 List start their index at 0 so [2] is the third element. But the last item is… print(example[-1]) >>>{“my”, “dictionary} We can slice them further. print(example[1:4]) #print 2nd to 5th element. >> [2, 2.45, [“i’am”, “a” “list inside”, “another”]] Slicing format example[start:stop:step] and we can go further if we know it’s list and lists, print(example[4][2]) >>>”list inside” Step will skip x amount hint in the list i.e. every 4th element. This can be done negatively as well. And reverse the list. We can loop directly through list… for element in example: if element == 2: break print(“No 2 in the list”) Or check with in if 2 in example: print(“There is a 2”) List can have comprehensions, we loved them so much we made them easier to make list_of_squares = [number**2 for number in range(5)] Lists are great because like all types they have useful methods. Such as, sort(), .append(), .insert(). You can easy check how many elements there are with len(). And since lists in Python can hold anything, anything, you can do a lot of complex requests coming from them. Lists are great for…loops. We want to do the same thing to a bunch of other things.
2 of 3
1
Thank you so much this has really helped
Programiz
programiz.com › python-programming › methods › built-in › list
Python list()
The list() constructor converts an iterable (dictionary, tuple, string etc.) to a list and returns it. text = 'Python' # convert string to list text_list = list(text) print(text_list) # check type of text_list print(type(text_list)) # Output: ['P', 'y', 't', 'h', 'o', 'n'] # <class 'list'>
Codecademy
codecademy.com › learn › ida-2-introduction-to-python › modules › ida-2-3-python-lists › cheatsheet
Introduction to Python: Lists in Python Cheatsheet | Codecademy
In order to add one item, create a new list with a single value and then use the plus symbol to add the list. ... In Python, lists are a versatile data type that can contain multiple different data types within the same square brackets.
Top answer 1 of 2
32
It's essentially a combination of tuple/list unpacking and *args iterable unpacking. Each iterable is getting unpacked on each iteration of the for loop.
First let's look at a simple tuple/list unpacking:
>>> x, y = (1, 2)
>>> x
1
>>> y
2
# And now in the context of a loop:
>>> for x, y in [(1, 2), (3, 4)]:
>>> print(f'x={x}, y={y}')
"x=1, y=2"
"x=3, y=4"
Now consider the following (and imagine the same concept within the loop as shown above):
>>> x, y = (1, 2, 3)
ValueError: too many values to unpack (expected 2)
>>> x, *y = 1, 2, 3
>>> x
1
>>> y
[2, 3]
Note how * allows y to consume all remaining arguments.
This is similar to how you would use * in a function - it allows an unspecified number of arguments and it consumes them all.
You can see more examples of (*args) usage here.
>>> def foo(x, *args):
>>> print(x)
>>> print(args)
>>>foo(1, 2, 3, 4)
1
[2, 3, 4]
As for practical examples, here is a quick one:
>>> names = ("Jack", "Johnson", "Senior")
>>> fist_name, *surnames = names
>>> print(surnames)
["Johnson", "Senior"]
2 of 2
1
Basically * indicates n number of countless elements.
Example :
x=1,2,4,6,9,8
print(type(x))
print(x)
Output:
<class 'tuple'>
(1, 2, 4, 6, 9, 8)
y,*x=1,2,4,6,9,8
print(type(x))
print(x)
Output:
<class 'list'>
[2, 4, 6, 9, 8]
Substack
mostlypython.substack.com › mostly python › python lists: a closer look
Python Lists: A closer look - by Eric Matthes
May 15, 2023 - It’s sometimes referred to more generally as a collection, but sequence is a better term because a list is an ordered collection. How we name something is important because an accurate name tells us what we can do with that thing. What would you expect to be able to do with a sequence? You’d probably expect to be able to create a sequence, grab items from it, add more items to it, remove some items, change the order of the items, and more. In Python, you can do all of these operations with most sequences, including lists.