How can I use for loop to build a dictionary that can reads values from a list?

Question

The first number is the student id, the second is the code of the course.

course = ["001, aly6015", "002, aly6050", "001, aly6020", "003, aly6070", "001, aly6140"]

dict = {}

for i in course:

I want to build a dictionary like the following: when I input dict['001'] then the output comes as aly6015, aly6020, aly6140

I don't know how to read value from the course list so that I can append 001, 002, 003 as keys in my dictionary and course code as values in my dictionary.

Thank you very much!

Answer 1

from collections import defaultdict

d = defaultdict(list)
for item in course:
    sid, cid = item.split(', ')
    d[sid].append(cid)

Answer 2

Try this

courses = ["001, aly6015", "002, aly6050", "001, aly6020", "003, aly6070", "001, aly6140"]
d = {}
for course in courses:
    key, value = course.split(",")
    if key in d:
        d[key].append(value)
    else:
        d[key] = [value]
print(d)

Output:

{'001': [' aly6015', ' aly6020', ' aly6140'], '002': [' aly6050'], '003': [' aly6070']}

Answer 3

You can split each course on ", " , then group withdict.setdefault :

courses = ["001, aly6015", "002, aly6050", "001, aly6020", "003, aly6070", "001, aly6140"]

d = {}
for course in courses:
    student_id, course_code = course.split(", ")
    d.setdefault(student_id, []).append(course_code)

print(d)
# {'001': ['aly6015', 'aly6020', 'aly6140'], '002': ['aly6050'], '003': ['aly6070']}

But its probably nicer to use collections.defaultdict , as shown by @Steven Rumbalski

Its also not a good idea to use dict as a variable name, as it shadows the builtin function dict()