Python Sort a list by multiple attributes with one line of code

Python Sort a list by multiple attributes with one line of code

Suppose we have a list of record

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records = (  (department, name, salary),  (department, name, salary),  ...  (department, name, salary) )

Then we want to sort the records first by 'department', and then by 'salary'

Maybe it would a little complex in other programming language. But in python, it would be as simple as one line as follows: 

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records.sort(  key = lambda l: (l[0], l[2]) )

I think this is the amazing part of functional programming that you can create an anonymous inline function to do this.  

Suppose we have another dictionary  { name: ages } linked with the records list,  we can also do sorting according to some external as follows : 

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record.sort(  key = lambda l:( l[0], dictionary_age(l[1]) ) )

If you want to rank the records in descending order, just set reverse = True; if you want to rank in a way that one attribute in descending order and one in ascending order, you have to a cmp function. 

Done!