How to sort list of names by first names while keeping it sorted by surnames (Python)?-CodePudding

I have a list of lists of names and surnames:

[['ARNO', 'ANN'], ['GATES', 'SOPHIA'], ['KERN', 'AMBER'], ['KORN', 'JACOB'], ['STAN', 'EMILY'], ['STAN', 'ANNA'], ['THORENSEN', 'VICTORIA'], ['WAHL', 'ALEXIS']]

I need to sort those with common surnames (ANNA and EMILY STAN) by their names within the given list. How to do it with Python?

CodePudding user response：

You can take advanted of the sorted method (docs here). Basically if you want your list sorted by surname first then:

x = [['ARNO', 'ANN'], ['GATES', 'SOPHIA'], ['KERN', 'AMBER'], ['KORN', 'JACOB'], ['STAN', 'EMILY'], ['STAN', 'ANNA'], ['THORENSEN', 'VICTORIA'], ['WAHL', 'ALEXIS']]    
sorted_list = sorted(x, key=lambda names: names[1])

if you want to sort by first name then:

x = [['ARNO', 'ANN'], ['GATES', 'SOPHIA'], ['KERN', 'AMBER'], ['KORN', 'JACOB'], ['STAN', 'EMILY'], ['STAN', 'ANNA'], ['THORENSEN', 'VICTORIA'], ['WAHL', 'ALEXIS']]    
sorted_list = sorted(x, key=lambda names: names[0])

CodePudding user response：

As the official documentation states, you can set-up sorting by multiple criterias, if your comparison function returns a tuple of multiple values. Hence, you can define your own sorting key, that will return 2 values, like (name, surname). This way, name will be used as a primary sorting criteria, surname - secondary. Your custom sorting key may look like this:

def custom_key(person: list) -> Tuple[str, str]:
    return (person[1], person[0])
# OR
custom_key = lambda person: (person[1], person[0])

It should be used like this:

sorted(people, key=custom_key)
# OR
sorted(people, key=lambda person: (person[1], person[0]))