[Tut] Python List max() - Printable Version

[Tut] Python List max() - Printable Version

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[Tut] Python List max() - xSicKxBot - 07-02-2020

Python List max()

Do you want to find the maximum of a Python list? This article gives you everything you need to know to master the max() function in Python.

Description

Python’s built-in max() function returns the maximum element of a list or its generalization (an iterable).

Syntax

The syntax of the max() function is as follows:

Code:
max(list, default=obj, key=func)

Arguments

Argument |
Description

Code:
list

|
The list or iterable from which you get the maximum value.

Code:
default

|
If the iterable is empty, returns this default object.

Code:
key

|
A function that associated a weight to each element in the iterable based on which the maximum is calculated.

Return Value

The return value of the

Code:
max(list)

function is a single element from the

Code:
list

that is the maximum of all elements. If the list is empty, the default object is returned, if explicitly defined. If not, a

Code:
ValueError

is thrown.

Examples

Let’s consider four examples that show how the arguments play together:

https://trinket.io/embed/python/7f277ce430

Exercise: Guess the output of the four print statements in the code. Run the code. How many did you guess right?

Maximum of List of Lists

Original article: How to Find the Maximum of a List of Lists?

To find the maximal list in a list of lists, you need to make two lists comparable. How? With the

Code:
key

argument of the

Code:
max()

function. The key argument is a function that takes one input (a list) and returns one output (a numerical value). The list with the largest numerical value is returned as the maximum of the list of lists.

Problem: Say you have a list of lists (nested list) and you want to find the maximum of this list. It’s not trivial to compare lists—what’s the maximum among lists after all? To define the maximum 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

Code:
[[1, 1, 1], [0, 2, 0], [3, 3, -1]]

. Which is the maximum element?

The first element of each inner list. The maximum is
Code:
[3, 3, -1]
.
The i-th element of each inner list (
Code:
i = 2
). The maximum is
Code:
[1, 1, 1]
.
The sum of inner list elements. The maximum is
Code:
[3, 3, -1]
.
The maximum of inner list elements. The maximum is
Code:
[3, 3, -1]
.
The minimum of inner list elements. The maximum is
Code:
[3, 3, -1]
.

So how do you accomplish this?

Solution: Use the

Code:
max()

function with key argument.

Let’s study the solution code for our different versions of calculating the maximum “list” of a list of lists (nested list).

Code:
lst = [[1, 1, 1], [0, 2, 0], [3, 3, -1]] # Maximum using first element
print(max(lst, key=lambda x: x[0]))
# [3, 3, -1] # Maximum using third element
print(max(lst, key=lambda x: x[2]))
# [1, 1, 1] # Maximum using sum()
print(max(lst, key=sum))
# [3, 3, -1] # Maximum using max
print(max(lst, key=max))
# [3, 3, -1] # Maximum using min
print(max(lst, key=min))
# [1, 1, 1]

Try it yourself in our interactive code shell:

https://repl.it/@finxter/maxlistoflists?lite=true

Related articles:

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