Understanding lambda's sort function in python -

i trying sort list of lists in python. have written following code:

def sort(intervals):     if intervals == [] : return []       intervals.sort(key = lambda x:x.start)     return intervals  = [[1,3],[8,10],[15,18],[2,6]] print(sort(a)) 

i getting following error:

attributeerror: 'list' object has no attribute 'start' 

please can explain lambda function sort , details above error. thank you!!

the reason error message sorting based on attribute not list (start not attribute of list'), quick fix is, either use sort method of list or use built-in method sorted:

1 - using sort method of list:

intervals.sort(key = lambda l:l[0]) 

2 - using built-in method sorted:

intervals = sorted(intervals, key=lambda l:l[0]) 

reading more sorting list in wiki post, interesting.