Sort List in Python

Posted by AbundantCode

In this article, you’ll learn how to sort a list with Python’s List sort() method.

The sort() method is used to sort a list:

list.sort()

The sort() method keeps the order of the original list. The sort() method changes the order of the elements in the list.

The less-than operator () is used by default in the sort() method to sort the members of a list. To put it another way, it prioritises the lower elements over the higher ones.

The reverse=True option to the sort() method is used to sort elements from higher to lower:

list.sort(reverse=True)

How to Sort List of Strings using Python List Sort method?

When a list contains strings, the sort() method alphabetizes the string elements.

The sort() method is used in the following example to order the elements in the guests list alphabetically:

guests = ['James', 'Mary', 'John', 'Patricia', 'Robert', 'Jennifer']
guests.sort()

print(guests)

Output

[‘James’, ‘Jennifer’, ‘John’, ‘Mary’, ‘Patricia’, ‘Robert’]

The next example utilises the sort() method with the reverse=True option to reverse the alphabetical order of the elements in the guests list:

guests = ['James', 'Mary', 'John', 'Patricia', 'Robert', 'Jennifer']
guests.sort(reverse=True)

print(guests)

Output

[‘Robert’, ‘Patricia’, ‘Mary’, ‘John’, ‘Jennifer’, ‘James’]

lambda expression

Python allows you to define a function without giving it a name using the following syntax:

lambda arguments: expression

An anonymous function is a function that has no name. A lambda expression is the name for this syntax.

It’s the technical equivalent of the following function:

def name(arguments):
    return expression

To sort the companies by revenue from low to high, use the lambda expression in the following example:

companies = [('Google', 2019, 134.81),
             ('Apple', 2019, 260.2),
             ('Facebook', 2019, 70.7)]

# sort the companies by revenue
companies.sort(key=lambda company: company[2])

# show the sorted companies
print(companies)

Output

[('Apple', 2019, 260.2), ('Google', 2019, 134.81), ('Facebook', 2019, 70.7)]
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