Sorting list of lists based on a given string in Python -

i have list of lists following:

list_of_lists = [    ('test_ss', 'test 1'),    ('test_2_ss', 'test 2'),    ('test_3_ss', 'test 3'),    ('test_ss', 'test 4') ] 

i need sort list of lists first item in each list based on given variable string.

as example, want sort 'test_ss' resulting list of lists be:

sorted_list_of_lists = [    ('test_ss', 'test 1'),    ('test_ss', 'test 4'),    ('test_2_ss', 'test 2'),    ('test_3_ss', 'test 3'), ] 

i've tried number of examples off , others (sorting list of lists based on list of strings, sorting lists based on particular element - python, sorting multiple lists based on single list in python, etc) haven't found right approach (or i've not been following examples correctly.

any pointers?

you can use simple key function this:

in [59]: def compare(element):    ....:     return element[0] == 'test_ss' or 99999    ....:   in [60]: sorted(list_of_lists, key=compare) out[60]:  [('test_ss', 'test 1'),  ('test_ss', 'test 4'),  ('test_2_ss', 'test 2'),  ('test_3_ss', 'test 3')]