i have 2d list implementation as follows. It shows no. of times every student topped in exams:-
list = main_record ['student1',1] ['student2',1] ['student2',2] ['student1',5] ['student3',3]
i have another list of unique students as follows:-
list = students_enrolled ['student1','student2','student3']
which i want to display student ranking based on their distinctions as follows:-
list = student_ranking ['student1','student3','student2']
What built in functions can be useful. I could not pose proper query on net. In other words i need python equivalent of following queries:-
select max(main_record[1]) where name = student1 >>> result = 5 select max(main_record[1]) where name = student2 >>> result = 2 select max(main_record[1]) where name = student3 >>> result = 3
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Answer
You define a dict base key of studentX and save the max value for each student key then sort the students_enrolled base max value of each key.
from collections import defaultdict
main_record = [['student1',1], ['student2',1], ['student2',2], ['student1',5], ['student3',3]]
students_enrolled = ['student1','student2','student3']
# defind dict with negative infinity and update with max in each iteration
tmp_dct = defaultdict(lambda: float('-inf'))
for lst in main_record:
k, v = lst
tmp_dct[k] = max(tmp_dct[k], v)
print(tmp_dct)
students_enrolled.sort(key = lambda x: tmp_dct[x], reverse=True)
print(students_enrolled)
Output:
# tmp_dct =>
defaultdict(<function <lambda> at 0x7fd81044b1f0>,
{'student1': 5, 'student2': 2, 'student3': 3})
# students_enrolled after sorting
['student1', 'student3', 'student2']