Python - Sorting a 2D array using each column

Question

I would like to sort a 2D array with three columns in the following fashion:

• First, the array goes through the one of the columns and sorts each number based on the value.
• Then, if there are any "ties", the program uses another column to sort out the ties.
• Finally, it uses the remaining column to sort out any ties still existing.

Example:

[[6, 0, "Hello"],
 [4, 1, "Jane"],
 [3, 0, "Text"],
 [4, 1, "Bob"]]

The columns in order of importance are: 1, 0, 2. This means we check the 2nd column, then the first, and finally the last.

[[6, 0, "Hello"],
 [3, 0, "Text"],
 [4, 1, "Jane"],
 [4, 1, "Bob"]]

Now, we use the first column:

[[3, 0, "Text"],
 [6, 0, "Hello"],
 [4, 1, "Jane"],
 [4, 1, "Bob"]]

Finally, we use the last column:

[[3, 0, "Text"],
 [6, 0, "Hello"],
 [4, 1, "Bob"],
 [4, 1, "Jane"]]

It is not hard to just sort it based on one column and disregard any duplicates. That is shown here: Sorting a 2D array using the second column C++. I tried data.sort(key=itemgetter(1)), but it only worked for one column.

I have no idea how to proceed with this. Please help!

Answer 1

from operator import itemgetter

data = [[6, 0, "Hello"],
        [4, 1, "Jane"],
        [3, 0, "Text"],
        [4, 1, "Bob"]]

data.sort(key=itemgetter(1, 0, 2))

print(data)  # [[3, 0, 'Text'], [6, 0, 'Hello'], [4, 1, 'Bob'], [4, 1, 'Jane']]

To help understand:

key_function = itemgetter(1, 0, 2)
print(key_function([6, 0, "Hello"]))  # (0, 6, 'Hello')