Loop through list of dictionaries if certain values to create a new list

I am working on a project off codecademy focusing on creating custom iterable classes and having trouble figuring out this section.

I have a list of dictionaries of students, example below:

student_roster = [
  {
    "name": "Karina M",
    "age": 8,
    "height": 48,
    "favorite_subject": "Math",
    "favorite_animal": "Dog"
  },
  {
    "name": "Yori K",
    "age": 7,
    "height": 50,
    "favorite_subject": "Art",
    "favorite_animal": "Cat"
  }, 
  {
    "name": "Alex C",
    "age": 7,
    "height": 47,
    "favorite_subject": "Science",
    "favorite_animal": "Cow"
   }]

What I need to do is iterate through the dictionaries in this list, and if a particular student’s "favorite_subject" is either "Math" or "Science", I need to grab their name and add them to a separate list.

I have tried multiple options and but I seem to keep adding EVERYONE to my new list, as the dictionary, rather than just grabbing only the value of their name to add to a list.

The end goal is to have a list:

stem = [Karina M, Alex C, etc]

I have tried a number of attempts, but for example, my most recent attempt. This is within the custom class created:

def get_students_with_subject(self): 
    stem = []
    for i in range(len(student_roster)): 
      for key, value in student_roster[i].items(): 
        if student_roster[i][key] == "Math" or "Science": 
          stem.append(student_roster[i])
        

When this runs, however, I am just adding every dictionary in my list to the new, stem list and it’s not parsing out the specific values.

I have also appended the stem list with:

stem.append(student_roster[i][key]) 

But that then adds all values from all dictionaries to the list and I can’t figure out how to add JUST the names of JUST the dictionaries that included "favorite_subject" == "Math" or "Science"

I am still learning so any help would be very appreciated.

>Solution :

First lets simplify the dictionaries in order to get the important data only:

student_roster = [
  {
    "name": "Karina M",
    "favorite_subject": "Math",
  },
  {
    "name": "Yori K",
    "favorite_subject": "Art",
  },
  {
    "name": "Alex C",
    "favorite_subject": "Science",
  }
]

Now that we have done that, we can start working on implementing a proper solution. First, go ahead and declare a new list:

math_and_science_students = []

That is the list where you will be adding the names of all the students that like math or science. Now lets work on the loop:

for student in student_roster:
    if student["favorite_subject"] in ["Math", "Science"]:
        math_and_science_students.append(student["name"])

The in operator in this case will check if the student favorite subject is Math or Science. It essentially is the same as saying:

if student["favorite_subject"] == "Math" or student["favorite_subject"] == "Science"

just much shorter, cleaner and more dynamic.