PYTHON

list sort by key python

>>> student_tuples = [
...     ('john', 'A', 15),
...     ('jane', 'B', 12),
...     ('dave', 'B', 10),
... ]
>>> sorted(student_tuples, key=lambda student: student[2])   
# sort by age
[('dave', 'B', 10), ('jane', 'B', 12), ('john', 'A', 15)]

sort list by key

# sort list by key
st1 = [ [ 1, 2], [3, 4], [4, 2], [ -1, 3], [ 4, 5], [2, 3]]
st1.sort()
print(st1)					# sort by  1st element [ [ -1, 3 ], [ 1, 2 ], [ 2, 3 ] ...
st1.sort(reverse=True)
print(st1)					# sort decending [ [ 4, 5 ], [ 3, 4], [ 2, 3 ] ...
st1.sort(key=lambda x: x[1])			# sort by 2nd element accending
print(st1)					# [ [ 1, 2 ], [ 4, 2 ], [ -1, 3 ] ...
st1.sort(key=lambda x: x[0] + x[1])		# sort by sum of 1st and 2nd element accending
print(st1)					# [ [ -1, 3 ], [ 1, 2 ], [ 2, 3 ] ...
# lambda undefined function
def sort_func(x) :				# classic way
	return x[0] + x[1]
st1.sort(key=sort_func)
st1.sort(key=lambda x: x[0] + x[1])		# defined function lambda at place

python sort array by key

# sort list by key
st1 = [ [ 1, 2], [3, 4], [4, 2], [ -1, 3], [ 4, 5], [2, 3]]
st1.sort()
print(st1)					# sort by  1st element [ [ -1, 3 ], [ 1, 2 ], [ 2, 3 ] ...
st1.sort(reverse=True)
print(st1)					# sort decending [ [ 4, 5 ], [ 3, 4], [ 2, 3 ] ...
st1.sort(key=lambda x: x[1])			# sort by 2nd element accending
print(st1)					# [ [ 1, 2 ], [ 4, 2 ], [ -1, 3 ] ...
st1.sort(key=lambda x: x[0] + x[1])		# sort by sum of 1st and 2nd element accending
print(st1)					# [ [ -1, 3 ], [ 1, 2 ], [ 2, 3 ] ...
# lambda undefined function
def sort_func(x) :				# classic way
	return x[0] + x[1]
st1.sort(key=sort_func)
st1.sort(key=lambda x: x[0] + x[1])		# defined function lambda at place