add new timezone and datetime example

mattmakai · mattmakai · commit 851ec57abcf8 · 2019-08-03T18:56:27.000-04:00
diff --git a/content/pages/examples/django/django-code-examples.markdown b/content/pages/examples/django/django-code-examples.markdown
@@ -36,6 +36,7 @@ output formats. Auditlog's source code is provided as open source under the
 Example code found in the AuditLog project:
 
 * [django.contrib.admin.filters SimpleListFilter](/django-contrib-admin-filters-simplelistfilter-examples.html)
+* [django.db.models DateTimeField](/django-db-models-datetimefield-examples.html)
 * [django.utils.html format_html](/django-utils-html-format-html-examples.html)
 
 
diff --git a/content/pages/examples/django/django-db-models-datetimefield.markdown b/content/pages/examples/django/django-db-models-datetimefield.markdown
@@ -98,3 +98,109 @@ class Device(models.Model):
 
 ## source code continues here without further DateTimeField examples
 ```
+
+
+## Example 2 from AuditLog
+[Auditlog](https://github.com/jjkester/django-auditlog) 
+([project documentation](https://django-auditlog.readthedocs.io/en/latest/))
+is a [Django](/django.html) app that logs changes to Python objects,
+similar to the Django admin's logs but with more details and
+output formats. Auditlog's source code is provided as open source under the
+[MIT license](https://github.com/jjkester/django-auditlog/blob/master/LICENSE).
+
+[**django-auditlog / src / auditlog / diff.py**](https://github.com/jjkester/django-auditlog/blob/master/src/auditlog/diff.py)
+
+```python
+from __future__ import unicode_literals
+
+from django.conf import settings
+from django.core.exceptions import ObjectDoesNotExist
+~~from django.db.models import Model, NOT_PROVIDED, DateTimeField
+from django.utils import timezone
+from django.utils.encoding import smart_text
+
+
+def track_field(field):
+    """
+    Returns whether the given field should be tracked by Auditlog.
+    Untracked fields are many-to-many relations and relations to 
+    the Auditlog LogEntry model.
+    :param field: The field to check.
+    :type field: Field
+    :return: Whether the given field should be tracked.
+    :rtype: bool
+    """
+    from auditlog.models import LogEntry
+    # Do not track many to many relations
+    if field.many_to_many:
+        return False
+
+    # Do not track relations to LogEntry
+    if getattr(field, 'remote_field', None) is not None and \
+        field.remote_field.model == LogEntry:
+        return False
+
+    # 1.8 check
+    elif getattr(field, 'rel', None) is not None and \
+        field.rel.to == LogEntry:
+        return False
+
+    return True
+
+
+def get_fields_in_model(instance):
+    """
+    Returns the list of fields in the given model instance. 
+    Checks whether to use the official _meta API or use the raw
+    data. This method excludes many to many fields.
+    :param instance: The model instance to get the fields for
+    :type instance: Model
+    :return: The list of fields for the given model (instance)
+    :rtype: list
+    """
+    assert isinstance(instance, Model)
+
+    # Check if the Django 1.8 _meta API is available
+    use_api = hasattr(instance._meta, 'get_fields') and \
+              callable(instance._meta.get_fields)
+
+    if use_api:
+        return [f for f in instance._meta.get_fields() if track_field(f)]
+    return instance._meta.fields
+
+
+def get_field_value(obj, field):
+    """
+    Gets the value of a given model instance field.
+    :param obj: The model instance.
+    :type obj: Model
+    :param field: The field you want to find the value of.
+    :type field: Any
+    :return: The value of the field as a string.
+    :rtype: str
+    """
+~~    if isinstance(field, DateTimeField):
+~~        # DateTimeFields are timezone-aware, so we need 
+~~        # to convert the field to its naive form before we 
+~~        # can accuratly compare them for changes.
+~~        try:
+~~            value = field.to_python(getattr(obj, field.name, 
+~~                                    None))
+~~            if value is not None and settings.USE_TZ and \
+~~                not timezone.is_naive(value):
+~~                value = timezone.make_naive(value, 
+~~                                            timezone=timezone.utc)
+~~        except ObjectDoesNotExist:
+~~            value = field.default if field.default \
+~~                is not NOT_PROVIDED else None
+    else:
+        try:
+            value = smart_text(getattr(obj, field.name, None))
+        except ObjectDoesNotExist:
+            value = field.default if field.default \
+                is not NOT_PROVIDED else None
+
+    return value
+
+## ... source file continues here without further DateTime examples ...
+```
diff --git a/content/pages/examples/django/django-utils-timezone.markdown b/content/pages/examples/django/django-utils-timezone.markdown
@@ -271,3 +271,108 @@ class EasyTimezoneMiddleware(middleware_base_class):
 ~~            timezone.deactivate()
 ```
 
+
+## Example 2 from AuditLog
+[Auditlog](https://github.com/jjkester/django-auditlog) 
+([project documentation](https://django-auditlog.readthedocs.io/en/latest/))
+is a [Django](/django.html) app that logs changes to Python objects,
+similar to the Django admin's logs but with more details and
+output formats. Auditlog's source code is provided as open source under the
+[MIT license](https://github.com/jjkester/django-auditlog/blob/master/LICENSE).
+
+[**django-auditlog / src / auditlog / diff.py**](https://github.com/jjkester/django-auditlog/blob/master/src/auditlog/diff.py)
+
+```python
+from __future__ import unicode_literals
+
+from django.conf import settings
+from django.core.exceptions import ObjectDoesNotExist
+from django.db.models import Model, NOT_PROVIDED, DateTimeField
+~~from django.utils import timezone
+from django.utils.encoding import smart_text
+
+
+def track_field(field):
+    """
+    Returns whether the given field should be tracked by Auditlog.
+    Untracked fields are many-to-many relations and relations to 
+    the Auditlog LogEntry model.
+    :param field: The field to check.
+    :type field: Field
+    :return: Whether the given field should be tracked.
+    :rtype: bool
+    """
+    from auditlog.models import LogEntry
+    # Do not track many to many relations
+    if field.many_to_many:
+        return False
+
+    # Do not track relations to LogEntry
+    if getattr(field, 'remote_field', None) is not None and \
+        field.remote_field.model == LogEntry:
+        return False
+
+    # 1.8 check
+    elif getattr(field, 'rel', None) is not None and \
+        field.rel.to == LogEntry:
+        return False
+
+    return True
+
+
+def get_fields_in_model(instance):
+    """
+    Returns the list of fields in the given model instance. 
+    Checks whether to use the official _meta API or use the raw
+    data. This method excludes many to many fields.
+    :param instance: The model instance to get the fields for
+    :type instance: Model
+    :return: The list of fields for the given model (instance)
+    :rtype: list
+    """
+    assert isinstance(instance, Model)
+
+    # Check if the Django 1.8 _meta API is available
+    use_api = hasattr(instance._meta, 'get_fields') and \
+              callable(instance._meta.get_fields)
+
+    if use_api:
+        return [f for f in instance._meta.get_fields() if track_field(f)]
+    return instance._meta.fields
+
+
+def get_field_value(obj, field):
+    """
+    Gets the value of a given model instance field.
+    :param obj: The model instance.
+    :type obj: Model
+    :param field: The field you want to find the value of.
+    :type field: Any
+    :return: The value of the field as a string.
+    :rtype: str
+    """
+    if isinstance(field, DateTimeField):
+        # DateTimeFields are timezone-aware, so we need 
+        # to convert the field to its naive form before we 
+        # can accuratly compare them for changes.
+~~        try:
+~~            value = field.to_python(getattr(obj, field.name, 
+~~                                    None))
+~~            if value is not None and settings.USE_TZ and \
+~~                not timezone.is_naive(value):
+~~                value = timezone.make_naive(value, 
+~~                                            timezone=timezone.utc)
+        except ObjectDoesNotExist:
+            value = field.default if field.default \
+                is not NOT_PROVIDED else None
+    else:
+        try:
+            value = smart_text(getattr(obj, field.name, None))
+        except ObjectDoesNotExist:
+            value = field.default if field.default \
+                is not NOT_PROVIDED else None
+
+    return value
+
+## ... source file continues here without further timezone examples ...
+```
diff --git a/content/pages/meta/00-change-log.markdown b/content/pages/meta/00-change-log.markdown
@@ -23,6 +23,8 @@ on GitHub.
     * [django.http Http404](/django-http-http404-examples.html)
 * Updated code examples on the following pages:
     * [django.contrib admin](/django-contrib-admin-examples.html)
+    * [django.db.models DateTimeField](/django-db-models-datetimefield-examples.html)
+    * [django.utils timezone](/django-utils-timezone-examples.html)
 
 ### July
 * Pushed the [3000th commit](https://github.com/mattmakai/fullstackpython.com/commit/180051047a582b9154874b15dccb315600f23300)
