How do you sort a nested list by specific strings that I pass into the sorted lambda?

Question

I've got a nested list which looks like:

mylist = [[123, "PASS"], [123, "FAIL"], [123, "N/A"]]

I have a sorted lambda to sort this alphabetically which looks like:

mylist = sorted(mylist, key=lambda x: (x[1]))

This works how I expected, but not what I want it to work like. This would return a list that when printed will have it like FAIL -> N/A -> PASS

Instead, I want PASS -> FAIL -> N/A, so not alphabetically, almost a custom sort. I have hundreds of pass elements, hundreds of fail elements and hundreds of N/A elements.

What is the best way to create a 'custom' sort based off strings that I expect to go in order.

Answer 1

You can do it with a dictionary:

sort_order = {'PASS': 0, 'FAIL': 1, 'N/A':2}
mylist = [[123, "PASS"], [123, "FAIL"], [123, "N/A"]]
mylist.sort(key=lambda val: sort_order[val[1]])
mylist

Output:

[[123, 'PASS'], [123, 'FAIL'], [123, 'N/A']]

Edit: Note that using mylist.sort(...) is (slightly) faster than reassigning mylist to sorted(...) as has been proposed by others.

Answer 2

You can specify the order:

order = ["PASS", "FAIL", "N/A"]                    # desired order of items
         
sorted(mylist, key = lambda x: order.index(x[1]))  # order based upon where 
                                                   #  x[1] is in order

Answer 3

use a lookup table - see below

lookup = {'PASS':0,'FAIL': 1,'N/A':2}

mylist = [[123, "PASS"], [123, "FAIL"], [123, "N/A"]]
mylist = sorted(mylist, key=lambda x: lookup[x[1]])
print(mylist)

output

[[123, 'PASS'], [123, 'FAIL'], [123, 'N/A']]

Answer 4

You can do this a bit "manually" by creating a new list using:

    newlist=[item for item in mylist if item[1]=='PASS']+[item for item in mylist if item[1]=='FAIL']+[item for item in mylist if item[1]=='N/A']