🔒 Simple list comprehension not working

[proven mica]

Hi, I'm writing a small script to automate some processes for testing purposes.

This is what the relevant part of my code looks like:

def demote_to_user(student_file: str):
    with open(student_file) as student_csv:
        students = [Student(login, int(matriculation_number), first_name, last_name)
                    for student_line in student_csv.readlines()[1:]
                    for login, matriculation_number, _, first_name, last_name in student_line.split(",")]


if __name__ == "__main__":
    demote_to_user("single_sample.csv")
```and here's the `single_sample.csv`:
```csv
login,matriculation number,email,firstname,lastname
user_51,00000051,[email protected],Tilda,Müller

This is the error I get:

Traceback (most recent call last):
  File "/home/samuel/PycharmProjects/PythonProject/main.py", line 120, in <module>
    demote_to_user("single_sample.csv")
  File "/home/samuel/PycharmProjects/PythonProject/main.py", line 89, in demote_to_user
    for login, matriculation_number, _, first_name, last_name in student_line.split(",")]
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
ValueError: too many values to unpack (expected 5)

I've ran this version of the code:

def demote_to_user(student_file: str):
    with open(student_file) as student_csv:
        for student_line in student_csv.readlines()[1:]:
            print(student_line)
            print(student_line.split(","))
            login, matriculation_number, _, first_name, last_name = student_line.split(",")
```and it works without any problems.


Now I know that I could just re-write it with that explicit for-loop, but I really want to keep the list comprehension in there, at this point it's just out of spite 🐒

[wispy helm]

@proven mica

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[paper ice]

hi

doing for ... in student_line.split(',') expects student_line.split(',') to look something like [(a, b, c, d, e), (f, g, h, i, j), ...] rather than [a, b, c, d, e]

you're not supposed to use a list comp to just destructure the tuple

[safe cedar]

                    for student_line in student_csv.readlines()[1:]
                    for login, matriculation_number, _, first_name, last_name in student_line.split(",")]

student_line.split(",") returns a list of strings, you can't really unpack that in a for loop

[proven mica]

Wait, so it just works if I do:

students = [Student(login, int(matriculation_number), first_name, last_name)
                    for student_line in student_csv.readlines()[1:]
                    for login, matriculation_number, _, first_name, last_name in [student_line.split(",")]]

no?

ah nvm

no, no it doesn't

or does it. wait

[paper ice]

it does, but it's not really best practice or readable

[safe cedar]

have you considered using the csv library?

with open("single_sample.csv", "r") as f:
  csvreader = csv.reader(f, delimiter=',')
  for login, matriculation_number, _, first_name, last_name in csvreader:
    ...

[bronze hamlet]

probably better off just writing the logic out in for loops first, then re-factor into comprehensions where it makes sense

[proven mica]

I tried to use that originally to write to the file when creating it (in another function def gen_random_students(amount_of_students: int, start_idx: int = 0, login_prefix: str = "user_", output_file: str = "random_students.csv", create_in_artemis: bool = False):), but ran into some issues and then completely switched to manual operation 🐒

[safe cedar]

we can help you fix it if you want

[proven mica]

Nah, it's fine. I've got the "manual operation" down to this:

class Student:
    login: str
    matriculation_number: str
    first_name: str
    last_name: str
    email: str = ""

    def __init__(self, login, matriculation_number: int, first_name, last_name):
        self.login = login
        self.matriculation_number = f"{matriculation_number:08}"
        self.first_name = first_name
        self.last_name = last_name
        self.email = f"{login}@artemis.org"

    @staticmethod
    def header():
        return "login,matriculation number,email,firstname,lastname"  # that's the header row

    def __repr__(self):
        return f'{self.login},{self.matriculation_number:08},{self.email},{self.first_name},{self.last_name}'  # print this into the file


# pseudo-code version of gen_random_students, as to not bother you with some minor details
def gen_random_students(...):
    with output_csv:
        output_csv.write(f"{Student.header()}\n")
        for i in range:
            random_student = Student(...)
            output_csv.write(f"{random_student}\n")

So yeah, it's not particularly clean I guess, but it works for my purposes.

But I actually found a small "bug" I forgot about rn:

students = [Student(login, int(matriculation_number), first_name, last_name)
            for student_line in (line.strip() for line in student_csv.readlines()[1:])
            for login, matriculation_number, _, first_name, last_name in [student_line.split(",")]]
```I need to put the `.strip()` in order to avoid copying the newline character after the last name

[tender holly]

@proven mica

Error Message: ValueError: too many values to unpack (expected 5)

[proven mica]

?

[tender holly]

first Use List Comprehension with Error Handling:

Adjust the comprehension to handle cases where the number of values may vary

try this ?

class Student:
def init(self, login, matriculation_number, first_name, last_name):
self.login = login
self.matriculation_number = matriculation_number
self.first_name = first_name
self.last_name = last_name

def demote_to_user(student_file: str):
with open(student_file) as student_csv:
students = [
Student(login, int(matriculation_number), first_name, last_name)
for student_line in student_csv.readlines()[1:]
if len(student_line.split(",")) == 5 # Ensure exactly 5 values
for login, matriculation_number, _, first_name, last_name in [student_line.split(",")]
]
return students # Return the list of students for further processing if needed

if name == "main":
students = demote_to_user("single_sample.csv")
# You can print or process the students list as needed
for student in students:
print(f"Login: {student.login}, Matriculation Number: {student.matriculation_number}, Name: {student.first_name} {student.last_name}")

[wispy helm]

Hey @tender holly!

Please edit your message to use a code block

```py
print('Hello, world!')
```

This will result in the following:

print('Hello, world!')```

[proven mica]

Did you read Rule #10 ?

[tender holly]

forgot sry class Student:
def init(self, login, matriculation_number, first_name, last_name):
self.login = login
self.matriculation_number = matriculation_number
self.first_name = first_name
self.last_name = last_name

def demote_to_user(student_file: str):
with open(student_file) as student_csv:
students = [
Student(login, int(matriculation_number), first_name, last_name)
for student_line in student_csv.readlines()[1:]
if len(student_line.split(",")) == 5 # Ensure exactly 5 values
for login, matriculation_number, _, first_name, last_name in [student_line.split(",")]
]
return students # Return the list of students for further processing if needed

if name == "main":
students = demote_to_user("single_sample.csv")
# You can print or process the students list as needed
for student in students:
print(f"Login: {student.login}, Matriculation Number: {student.matriculation_number}, Name: {student.first_name} {student.last_name}")

WAIT HWAT

[proven mica]

Rule 10
Do not copy and paste answers from ChatGPT or similar AI tools.

[tender holly]

who does

[proven mica]

You

[tender holly]

i didnt

[proven mica]

LMFAO

Did you just post the entire ChatGPT reply by accident?

[tender holly]

nope

its not chat gpt

its brain gpt

xD

.

😭

im just too lazy to help ppls rn

ppl*

[proven mica]

I'm just curious cause you apparently have not read the immediate answers, do not know how to format code on Discord, and frankly, noone would write like this:

first Use List Comprehension with Error Handling:
Adjust the comprehension to handle cases where the number of values may vary

Like, you saw my specific input file, and I know that will never change, so I don't need to worry about length verification. If something doesn't work I'd much rather get an aggressive error, rather than sweeping it under the rug.

Also your suggestion would completely remove any reason for demote_to_user to carry that name. Basically "you" rewrote it into a read_students_from_csv file.

[proven mica]

What? So is that a "confession" that you did in fact use ChatGPT? I'm confused.

Also if you don't want to help others/are too lazy, then just... don't help.

[safe cedar]

it seems like we already solved their issue, so i'm not sure what the point of sending this is

[tender holly]

bro

idk what im typing

i just came here

did random things

xD

[safe cedar]

in the future i would advice familiarizing yourself with your environment and the etiquette of the community before engaging in online spaces

[tender holly]

erm

[proven mica]

!close

[wispy helm]

Python help channel closed with !close

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