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Python Using Databases in Python Meet Peewee Queries Are Your Friend

Posted by Tim Balzer
Tim Balzer
13,315 Points

Why am I receiving an InternalError when trying to handle the IntegrityError?

Rather than working in the Workspace, I set up peewee to use my local PostgreSQL database. However, I receive an InternalError when I try to handle the IntegrityError in this exercise.

Code:

def add_students():
    for student in students:
        try:
            Student.create(username=student["username"],
                           points=student["points"])
        except IntegrityError:
            student_record = Student.get(username=student["username"])
            student_record.points = student["points"]
            student_record.save()

Error:

peewee.InternalError: current transaction is aborted, commands ignored until end of transaction block

2 Answers

Tim Balzer
Tim Balzer
13,315 Points

The way to get around this was to actually to rollback the transaction before continuing. Here's what ended up working for me:

def add_students():
    for student in students:
        try:
            Student.create(username=student["username"],
                           points=student["points"])
        except IntegrityError:
            db.rollback()
            student_record = Student.get(username=student["username"])
            student_record.points = student["points"]
            student_record.save()
Yeeka Yau
Yeeka Yau
7,410 Points
Yeeka Yau
Yeeka Yau
7,410 Points

Thanks for posting this, I am doing the same thing on my local machine with postgresql. I had the exact same problem.

Kenneth Love
STAFF
Kenneth Love
Treehouse Guest Teacher
Kenneth Love
Kenneth Love
Treehouse Guest Teacher

Hmm, interesting. I'm guessing that the .create() got Postgres into a weird state, but it doesn't seem like it should have.

Jack Fuller
Jack Fuller
5,859 Points
Jack Fuller
Jack Fuller
5,859 Points

Did anyone get to the bottom of his? I've just spent an hour trying to work out why the exception didn't just catch without the rollback.

Sorry for the long post.

Traceback (most recent call last):
  File "/Users/jackfuller/python/databases/databasing/lib/python3.6/site-packages/peewee.py", line 3748, in execute_sql
    cursor.execute(sql, params or ())
psycopg2.IntegrityError: duplicate key value violates unique constraint "student_username"
DETAIL:  Key (username)=(james) already exists.


During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "student.py", line 32, in add_students
    points=student['points'])
  File "/Users/jackfuller/python/databases/databasing/lib/python3.6/site-packages/peewee.py", line 4889, in create
    inst.save(force_insert=True)
  File "/Users/jackfuller/python/databases/databasing/lib/python3.6/site-packages/peewee.py", line 5082, in save
    pk_from_cursor = self.insert(**field_dict).execute()
  File "/Users/jackfuller/python/databases/databasing/lib/python3.6/site-packages/peewee.py", line 3506, in execute
    cursor = self._execute()
  File "/Users/jackfuller/python/databases/databasing/lib/python3.6/site-packages/peewee.py", line 2892, in _execute
    return self.database.execute_sql(sql, params, self.require_commit)
  File "/Users/jackfuller/python/databases/databasing/lib/python3.6/site-packages/peewee.py", line 3755, in execute_sql
    self.commit()
  File "/Users/jackfuller/python/databases/databasing/lib/python3.6/site-packages/peewee.py", line 3578, in __exit__
    reraise(new_type, new_type(*exc_args), traceback)
  File "/Users/jackfuller/python/databases/databasing/lib/python3.6/site-packages/peewee.py", line 135, in reraise
    raise value.with_traceback(tb)
  File "/Users/jackfuller/python/databases/databasing/lib/python3.6/site-packages/peewee.py", line 3748, in execute_sql
    cursor.execute(sql, params or ())
peewee.IntegrityError: duplicate key value violates unique constraint "student_username"
DETAIL:  Key (username)=(james) already exists.

The above ran twice before printing this line and exiting: 

peewee.InternalError: current transaction is aborted, commands ignored until end of transaction block