Say, you want to convert a list of lists lst=[[1, 2], [3, 4]] into a single list [1, 2, 3, 4]. How to achieve this? There are different options:
- List comprehension
[x for l in lst for x in l]assuming you have a list of listslst. - Unpacking
[*lst[0], *lst[1]]assuming you have a list of two listslst. - Using the
extend()method of Python lists to extend all lists in the list of lists.
Find examples of all three methods in the following code snippet:
lst = [[1, 2], [3, 4]]
# Method 1: List Comprehension
flat_1 = [x for l in lst for x in l]
# Method 2: Unpacking
flat_2 = [*lst[0], *lst[1]]
# Method 3: Extend Method
flat_3 = []
for l in lst:
flat_3.extend(l)
## Check results:
print(flat_1)
# [1, 2, 3, 4]
print(flat_2)
# [1, 2, 3, 4]
print(flat_3)
# [1, 2, 3, 4]Due its simplicity and efficiency, the first list comprehension method is superior to the other two methods.
You can check out these methods yourself in our interactive code shell:
Do you need to dive even deeper into this code snippet? Try the Python teacher code execution to see the memory objects created by this code:
Where to Go From Here?
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