Short answer: To find the minimal list in a list of lists, you need to make two lists comparable. How? With the
key argument of the
min() function. The key argument is a function that takes one input (a list) and returns one output (a numerical value). The list with the smallest numerical value is returned as the minimum of the list of lists.
Problem: Say you have a list of lists (nested list) and you want to find the minimum of this list. It’s not trivial to compare lists—what’s the minimum among lists after all? To define the minimum among the inner lists, you may want to consider different objectives.
- The first element of each inner list.
- The i-th element of each inner list.
- The sum of inner list elements.
- The maximum of inner list elements.
- The minimum of inner list elements.
Example: Given list of lists
[[1, 1, 1], [0, 2, 0], [3, 3, -1]]. Which is the minimum element?
- The first element of each inner list. The minimum is
[0, 2, 0].
- The i-th element of each inner list (
i = 2). The minimum is
3, 3, -1]
- The sum of inner list elements. The minimum is
0, 2, 0]
- The maximum of inner list elements. The minimum is
[1, 1, 1].
- The minimum of inner list elements. The minimum is
[3, 3, -1].
So how do you accomplish this?
Solution: Use the
min() function with key argument.
min() function is a built-in function in Python (Python versions 2.x and 3.x). Here’s the syntax:
|The values among which you want to find the minimum. In our case, it’s a list of lists.|
|(Optional. Default |
Let’s study the solution code for our different versions of calculating the minimal “list” of a list of lists (nested list).
Try it yourself in our interactive code shell:
lst = [[1, 1, 1], [0, 2, 0], [3, 3, -1]] # Minimum using first element print(min(lst, key=lambda x: x)) # [0, 2, 0] # Minimum using third element print(min(lst, key=lambda x: x)) # [3, 3, -1] # Minimum using sum() print(min(lst, key=sum)) # [0, 2, 0] # Minimum using max print(min(lst, key=max)) # [1, 1, 1] # Minimum using min print(min(lst, key=min)) # [3, 3, -1]
- How to Find the Max of List of Lists in Python?
- Python List Methods [Overview]
- Python List sort() – The Ultimate Guide
- Python Lists – Everything You Need to Know to Get Started
- Key with Maximum Value in Dict
- Key with Minimum Value in Dict
Where to Go From Here?
Enough theory. Let’s get some practice!
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