Python: List of tuples-CodePudding

Please, if I have a list of tuples, say:

list = [('James', 27, 2000), ('Aaron', 24, 1290), ('Max', 23, 2300), ('Ben', 27, 1900)]

How do I get all the names in ascending order?
How do I get a list that shows the tuples in ascending order of names?

Thanks

CodePudding user response：

If you sort a list of tuples, by default the first item in the tuple is taken as the key. Therefore:

list_ = [('James', 27, 2000), ('Aaron', 24, 1290), ('Max', 23, 2300), ('Ben', 27, 1900)]

for name, *_ in sorted(list_):
    print(name)

Output:

Aaron
Ben
James
Max

Or, if you want the tuples then:

for t in sorted(list_):
    print(t)

...which produces:

('Aaron', 24, 1290)
('Ben', 27, 1900)
('James', 27, 2000)
('Max', 23, 2300)

CodePudding user response：

Assuming by ascending you mean alphabetical? You can do it with sorted:

a = [('James', 27, 2000), ('Aaron', 24, 1290), ('Max', 23, 2300), ('Ben', 27, 1900)]
sorted(a, key=lambda x: x[0])

Output:

[('Aaron', 24, 1290),
 ('Ben', 27, 1900),
 ('James', 27, 2000),
 ('Max', 23, 2300)]

CodePudding user response：

lst = [('James', 27, 2000), ('Aaron', 24, 1290), ('Max', 23, 2300), ('Ben', 27, 1900)]

print(sorted(lst))

Prints

[('Aaron', 24, 1290), ('Ben', 27, 1900), ('James', 27, 2000), ('Max', 23, 2300)]

CodePudding user response：

list = [('James', 27, 2000), ('Aaron', 24, 1290), ('Max', 23, 2300), ('Ben', 27, 1900)]

sorted_names = sorted([i[0] for i in list])
print(sorted_names)

Output:

['Aaron', 'Ben', 'James', 'Max']

sorted_by_name = sorted(list, key=lambda tup: tup[0])
print(sorted_by_name)

Output:

[('Aaron', 24, 1290), ('Ben', 27, 1900), ('James', 27, 2000), ('Max', 23, 2300)]

CodePudding user response：

>>> l = [('James', 27, 2000), ('Aaron', 24, 1290), ('Max', 23, 2300), ('Ben', 27, 1900)]
>>> sorted([name for name, _, _ in l])
['Aaron', 'Ben', 'James', 'Max']
>>> sorted(l)
[('Aaron', 24, 1290), ('Ben', 27, 1900), ('James', 27, 2000), ('Max', 23, 2300)]

Be advised that list is an object in Python, so when you create a variable with the name list, you overwrite that reference and you cannot use list(something) after in your program.

CodePudding user response：

You can use key parameter in sort or sorted function. Here's an example:

my_list = [('James', 27, 2000), ('Aaron', 24, 1290), ('Max', 23, 2300), ('Ben', 27, 1900)]
my_list_sorted_by_names = sorted(my_list, key=lambda x: x[0])

And the result will be:

[('Aaron', 24, 1290), ('Ben', 27, 1900), ('James', 27, 2000), ('Max', 23, 2300)]

You can use list comprehension to extract names from sorted list:

ordered_names = [i[0] for i in my_list_sorted_by_names]