Filtering though a list (Python)

I'm a beginner at Python and I am doing this exercise which reads:

"Define the function Students_at_level that takes a list of Students and a string (representing a class level, e.g., 'FR' or 'SO') and returns a list of students whose class level matches the parameter."

I was given this code:

from collections import namedtuple
Course = namedtuple('Course', 'dept num title instr units')
# Each field is a string except the number of units
ics31 = Course('ICS', '31', 'Intro to Programming', 'Kay', 4.0)
ics32 = Course('ICS', '32', 'Programming with Libraries', 'Thornton', 4.0)
wr39a = Course('Writing', '39A', 'Intro Composition', 'Alexander', 4.0)
wr39b = Course('Writing', '39B', 'Intermediate Composition', 'Gross', 4.0)
bio97 = Course('Biology', '97', 'Genetics', 'Smith', 4.0)
mgt1  = Course('Management', '1', 'Intro to Management', 'Jones', 2.0)

Student = namedtuple('Student', 'ID name level major studylist')
# All are strings except studylist, which is a list of Courses.
sW = Student('11223344', 'Anteater, Peter', 'FR', 'PSB', [ics31, wr39a, bio97, mgt1])
sX = Student('21223344', 'Anteater, Andrea', 'SO', 'CS', [ics31, wr39b, bio97, mgt1])
sY = Student('31223344', 'Programmer, Paul', 'FR', 'COG SCI', [ics32, wr39a, bio97])
sZ = Student('41223344', 'Programmer, Patsy', 'SR', 'PSB', [ics32, mgt1])

StudentBody = [sW, sX, sY, sZ]

So far I have this code as an attempt to solve this:

def Students_at_level(students: list, level: str) -> list:
    ''' takes a list of Students and a string, returns students
    of matching parameter'''
    for i in students:
        if level == Student.level:
            return i
assert(Students_at_level([sW, sX, sY, sZ], 'FR') == [sW, sY])

This isn't working. Can anyone guide me in the right direction? Thanks.

Answers


It should be helpful:

In [1]: mylist = [12, 34, "FR", "Something", "SO"]
In [2]: [i for i in mylist if i in ('FR', 'SO')]
Out[2]: ['FR', 'SO']

Or use filter for more enhance filter condition:

In [4]: filter(lambda i: i in ('FR', 'SO'), mylist)
Out[4]: ['FR', 'SO']

you could use simple list comprehension for this kind of task, example:

>>> a = range(10)
>>> a
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> [i for i in a if i == 2 or i == 1 ]
[1, 2]
>>>

As the comment indicates, your function Students_at_level takes a list of Students and a string, and it returns a list of students.

But, you are returning i which is of type Student:

for i in students:
    if level == Student.level:
        return i

(I guess you wanted to write i.level instead of Student.level)

You can either change the function into a generator:

def Students_at_level(students, level):
    for i in students:
        if level == i.level:
            yield i

Or simply return a list as intended in the first place. The easy to understand solution would be:

def Students_at_level(students, level):
    r = []
    for i in students:
        if level == i.level:
            r.append(i)
    return r

And the Pythonic way to do it is using a list comprehension:

def Students_at_level(students, level):
    return [i for i in students if level == i.level]

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