Sorting list by multiple methods

Question

I have a list of flights, which are to be sorted on departure date first, and then to be sorted on the total flight duration, keeping their order according to the date.

• Calling the departure date is a method of the "Flight" object.
• Calling the flight duration is also a method of the "Flight" object.

output should be:

• 04-07-2017 flighttime: 05:00
• 04-07-2017 flighttime: 06:00
• 05-07-2017 flighttime: 04:00
• 05-07-2017 flighttime: 05:00

I tried:

sorted(flights, key=methodcaller('date','flighttime'))

but methodcaller only takes 1 argument. I tried also groupby first and then sort on flighttime, but then the list gets sorted to flighttime only.

thank you

Answer 1

methodcaller cannot call more than 1 method, the other arguments are parameters:

f = methodcaller('name', 'foo', bar=1), the call f(b) returns b.name('foo', bar=1)

So it can be done using methodcaller but in a more complex way probably involving lambda like (untested) lambda x : methodcaller('name')(x),methodcaller('flighttime')(x)

So I would use a simple lambda instead (where x is a Flight object):

sorted(flights, key=lambda x : (x.date(),x.flighttime()))