id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
22268	Document values_list() behavior for ManyToManyField	Kal Sze	Mikkel Bach Mortensen	"Suppose you have a `schools` app, with these model definitions:

{{{
from django.db import models

class School(models.Model):
    name = models.CharField(unique=True, max_length=255)

class Class(models.Model):
    school = models.ForeignKey(School)
    name = models.CharField(unique=True, max_length=255)
    students = models.ManyToManyField('Student')

class Student(models.Model):
    surname = models.CharField(max_length=255)
    given_name = models.CharField(max_length=255)
}}}

Now, try this in the Django shell:
{{{
$ python manage.py shell

>>> from schools.models import School, Class, Student

# Create the school
>>> concordia = School(name='Concordia University')
>>> concordia.save()

# Create the Software Engineering class
>>> soen = Class(school=concordia, name='Software Engineering')
>>> soen.save()

# Create the Computer Engineering class
>>> coen = Class(school=concordia, name='Computer Engineering')
>>> coen.save()

# Create a student
>>> john_smith = Student(surname='Smith', given_name='John')
>>> john_smith.save()

# Add this student into one of the classes
>>> soen.students.add(john_smith)

# Now make a query using values_list
>>> students = Class.objects.values_list('students', flat=True)

# How many students are there supposed to be in this `students` QuerySet?
>>> print students.count()
1

# What if we iterate over it?
>>> for s in students:
>>>     print s
1
None

# Wait, what!?
>>> print len(list(students))
>>> 2
}}}"	Cleanup/optimization	closed	Documentation	dev	Normal	fixed	orm, values_list, ManyToManyField	anubhav9042@… pirosb3 saivnm5@…	Ready for checkin	1	0	0	0	1	0