To create an empty list in Python, you can use two ways. First, the empty square bracket notation [] creates a new list object without any element in it. Second, the list() initializer method without an argument creates an empty list object too.
Both approaches are shown in the following code:
# Way 1 to create an empty list: my_list = [] # Way 2 to create an empty list: my_list = list()
Next, you’ll learn many more related Python concepts you need to know that concern creation of lists. Keep reading to keep improving your skills and answer any subsequent question you may have!
Python list() — Quick Guide
Python’s built-in list() function creates and returns a new list object. When used without an argument, it returns an empty list. When used with the optional iterable argument, it initializes the new list with the elements in the iterable.
You can create an empty list by skipping the argument:
>>> list() []
If you pass an iterable—such as another list, a tuple, a set, or a dictionary—you obtain a new list object with list elements obtained from the iterable:
>>> list([1, 2, 3]) [1, 2, 3]
🌍 Read More: Read our full tutorial on the Finxter blog to learn everything you need to know.
Python Create Empty List of Size
To create a list of n placeholder elements, multiply the list of a single placeholder element with n.
For example, use [None] * 5 to create a list [None, None, None, None, None] with five elements None.
You can then overwrite some elements with index assignments.
In the example, lst[2] = 42 would result in the changed list [None, None, 42, None, None].
# Create a list with n placeholder elements n = 5 lst = [None] * n # Print the "placeholder" list: print(lst) # [None, None, None, None, None] # Overwrite the placeholder elements lst[0] = 'Alice' lst[1] = 0 lst[2] = 42 lst[3] = 12 lst[4] = 'hello' print(lst) # ['Alice', 0, 42, 12, 'hello']
🌍 Read More: Read our full tutorial on the Finxter blog to learn everything you need to know.
Python Create Empty List of Lists
You can create an empty list of lists do not use [[]] * n because this creates a nested list that contains the same empty list object n times which can cause problems because if you update one, all inner lists change!
To create an empty list of lists with n empty inner lists, use the list comprehension statement [[] for _ in range(n)] that creates a fresh empty list object n times.
n = 5 my_list = [[] for _ in range(n)] print(my_list) # [[], [], [], [], []]
List comprehension is a powerful Python feature and I’ve written a full blog tutorial on it—feel free to watch my general explainer video and read the associated blog article!
🌍 Read More: Read our full tutorial on the Finxter blog to learn everything you need to know.
Python Create Empty List and Append in Loop
Follow these three easy steps to create an empty list and append values to it in a for loop:
my_list = []creates the empty list and assigns it to the namemy_list.for i in range(10):initializes the for loop to be repeated 10 times using loop variableithat takes on all values between 0, 1, …, 9.my_list.append(i)is the loop body that appends the integer value of the loop variableito the list.
Here’s the code example:
my_list = []
for i in range(10):
my_list.append(i)
print(my_list)
# [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]However, a better Python one-liner alternative is using list comprehension for this:
my_list = [i for i in range(10)]
Python Create List of Empty Strings
To create a list of n empty strings, you can use the expression [''] * n because it places the same empty string literal '' into the list n times. This doesn’t cause any problems due to the fact that all list elements refer to the same empty string object because strings are immutable and cannot be modified anyways.
>>> [''] * 5 ['', '', '', '', ''] >>> [''] * 20 ['', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '']
Python Create Empty List of Dictionaries
To create a list of n dictionaries, each dict being empty, use the list comprehension statement [dict() for _ in range(n)] with the underscore _ as a throw-away “loop variable” and the dict() built-in dictionary creation function.
my_list = [dict() for _ in range(10)]
print(my_list)
# [{}, {}, {}, {}, {}, {}, {}, {}, {}, {}]
Note that if you update one of the dictionaries, all other dictionaries are unaffected by this because we really created n independent dictionary objects.
# update first dictionary:
my_list[0]['foo'] = 'bar'
print(my_list)
# [{'foo': 'bar'}, {}, {}, {}, {}, {}, {}, {}, {}, {}]Python Create Empty List of Class Objects
To create an empty list of class objects, you can use list comprehension statement my_list = [MyClass() for _ in range(n)] that repeats n times the creation of an empty class object MyClass and adding it to the list. You can then later change the contents of the n different MyClass objects.
class MyClass(object):
pass
my_list = [MyClass() for _ in range(5)]
print(my_list)
# [<__main__.MyClass object at 0x000001EA45779F40>, <__main__.MyClass object at 0x000001EA47533D00>, <__main__.MyClass object at 0x000001EA475334C0>, <__main__.MyClass object at 0x000001EA4758E070>, <__main__.MyClass object at 0x000001EA4758E4F0>]Python Create Empty List of Type
Python is a dynamic language so there is no concept of a “list of type X”. Instead of creating a list of a fixed type, simply create an empty list using [] or list() and assign it to a variable such as my_list. Using the variable, you can then fill into the existing list any data type you want!
Here we create an empty list and fill in an integer, a list, and a string—all into the same list!
my_list = []
# Alternative: my_list = list()
# Add integer to list:
my_list.append(42)
# Add list to list:
my_list.append([1, 2, 3])
# Add string to list:
my_list.append('hello world')
# Print all contents of list:
print(my_list)
# [42, [1, 2, 3], 'hello world']Python Create Empty List of Integers
To initialize a list with certain integers such as zeroes 0, you can either use the concise list multiplication operation [0] * n or you use list comprehension [0 for _ in range(n)].
>>> [0] * 5 [0, 0, 0, 0, 0] >>> [0] * 10 [0, 0, 0, 0, 0, 0, 0, 0, 0, 0] >>> [42] * 5 [42, 42, 42, 42, 42] >>> [42 for _ in range(5)] [42, 42, 42, 42, 42]
Python Create Empty List of Tuples
To create an empty list and later add one tuple at-a-time to it, first initialize the empty list using the [] square bracket operator and then use the list.append(t) to append one tuple t at a time.
Here we add three tuples to the initially empty list:
# create empty list:
my_list = []
# append tuples
my_list.append((1, 2))
my_list.append(('alice', 'bob', 'carl'))
my_list.append(tuple())
print(my_list)
# [(1, 2), ('alice', 'bob', 'carl'), ()]
Thanks, for reading through the whole article! If you learned something new, maybe you want to read our article on a similar but slightly different topic here:
👉 Recommended Tutorial: How to Return an Empty List from a Function in Python?
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