[The following is a series of debugging exercises that you may encounter in the real world of development. They are based on problems I have been asked. I thought it would be fun to share them.]
It is your first week at your new job as a software developer. You have your environment set up and you're seated beside a fellow junior who started a few days before you.
He turns to you and asks if you have a minute.
"Hey if you don't mind, please help me find out what's wrong..."
Problem 1
Context
To change display name of Model Instances, we will use def __str__() function in a model. The str function in a django model returns a string that is exactly rendered as the display name of instances for that model.
For example, if we adjust a model in models.py like so
from django.db import models
from django.db.models import Model
class SomeModel(Model):
name = models.CharField(max_length = 100)
def __str__(self):
return f"{self.name}"
When we access SomeModel.objects.all(), the output should be a list of the name fields of this object.
Problem
It doesn't work for comments. When a Comment object is printed, it shows [Comment object (1)] rather than what is defined under str.
Let's check the code:
# imports here
class Listing(models.Model):
max_bid = models.DecimalField(...)
...
def __str__(self):
return ...
class Bid(models.Model):
...
class User(AbstractUser):
...
class Comment(models.Model):
comment = models.TextField()
listing = models.ForeignKey(Listing, on_delete=models.CASCADE)
user = models.ForeignKey(User, on_delete=models.CASCADE)
def _str__(self):
return f'{self.id}: {self.comment}'
Where did your fellow teammate go wrong?
Problem 2
Context
Your coworker was secretly interviewing with other companies and was told to find the min value in a list without using min.
Problem
The below code doesn't seem to find the minimum element in the list. Why?
def minimum(some_list):
a = 0
for x in range(1, len(some_list)):
if some_list[x] < a:
a = some_list[x]
return a
Where did your fellow teammate go wrong?
Latest comments (5)
He used a single underscore instead of a double underscore. But I guess most code editors will indicate it is an error.
So it should be:
def str(self):
return f'{self.id}: {self.comment}'
It should be
a = some_list[0]
for x in range(len(some_list)):
pass
Should be <=.
Your teammate should change line 2 of the code from "a = 0" to "a = some_list[ 0 ]
You also need to change the range from "range(1, len(some_list))" to "range(len(some_list))"