Working Ninja
2018-09-26T20:30:58

By default, a ModelForm is populated with all its objects from the database. Sometimes it's desirable to limit these results as they are returned to the view. After setting up our ModelForm (forms.py) there is only one thing we need to do to make this happen. Within our view ...

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2018-08-19T10:21:07

Create unicode string "a".

>>> a = u'\u2019'
>>> a
u'\u2019'

Convert to ASCII string (ASCII is default for Python 2 str()).

>>> str(a)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
UnicodeEncodeError: 'ascii' codec can't encode character u'\u2019' in position 0: ordinal ...

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2018-07-27T22:37:04

Let's say we want to query our Polls app for all Questions that have popular (more than 5 votes) choices that contain Python in the choice_text.

We could query our database as follows:

SELECT * FROM question JOIN (SELECT * FROM choice WHERE vote_count > 5 AND choice_text LIKE '%Python%') choice ON ...

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2018-07-25T21:21:23

Here's the most straightforward and succinct way I've found to mock patch a function that returns different (but specific) results with each call, shamelessly copied from Python Docs:

>>> values = {'a': 1, 'b': 2, 'c': 3}
>>> def side_effect(arg):
...     return values[arg]
...
>>> mock.side_effect = side_effect
>>> mock('a ...

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2018-06-29T20:53:23

After updating mysql-connector-python to 8.0.11 (released April 19, 2018), I received an "OperationalError: 1043 (08S01): Bad handshake" error when querying a MySQL database. I found that I needed to set 'use_pure: True' in the connection string.

From the MySQL folks:

The C extension was ...

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2018-04-22T10:50:51

If you've ever touched a date or time related field via the Django API, you'll have noticed the big warning that the date and/or time is not localized. While the warning is nice there isn't much more in the way of how to localize the time. Here are two ...

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2016-01-11T21:47:37

Print all digits in a string as one integer:

>>> string = "a1b2c3"
>>> integer = int(filter(str.isdigit, string))
>>> print integer
123
>>> type(integer)
<type 'int'>

Or, if you would like a list of all digits:

>>> string = "a1b2c3"
>>> import re
>>> integer_list = re.findall('\d ...

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2016-02-04T08:04:04
class AbstractClass(models.Model):
    common_attribute = models.CharField()

    class Meta:
        abstract = True


class SpecializedClass(models.Model):
    specialized_attribute = models.CharField()

    class Meta:
        abstract = True


class AnotherSpecializedClass(models.Model):
    another_specialized_attribute = models.CharField()

    class Meta:
        abstract = True


class MultipleInheritance(AbstractClass, SpecializedClass):
    pass


class TripleMulitpleInheritance(AbstractClass, SpecializedClass, AnotherSpecializedClass):
    pass

Sources: https://docs.djangoproject.com/en ...

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2016-08-29T22:49:43

Set the end date with the current date and time and the start date 1 week prior:

import datetime

start_date = datetime.datetime.now() - datetime.timedelta(days=7)
end_date = datetime.datetime.now()

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2016-09-06T07:51:45
#!/usr/bin/env python

import os

os.environ['DJANGO_SETTINGS_MODULE'] = 'mysite.settings'

import django
django.setup()

from app.models import Class

# Your scripting here.

Sources:
https://docs.djangoproject.com/en/1.10/intro/tutorial02/#playing-with-the-api
https://docs.djangoproject.com/en/1.10/topics/settings/#on-the-server-mod-wsgi

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2016-11-03T20:05:28
import json
import psycopg2
from psycopg2.extras import RealDictCursor

cursor = conn.cursor(cursor_factory=RealDictCursor)
objects = cursor.fetchall()

print json.dumps(objects, indent=2)

# Django
#JsonResponse({'objects': objects})

Source: https://www.peterbe.com/plog/from-postgres-to-json-strings

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2016-11-11T16:55:21
import json

polls = Poll.objects.all()

# Convert our QuerySet into a list so polls can be serialized
print json.dumps(list(p), indent=2)
JsonResponse({'polls': list(polls)})

Source: http://stackoverflow.com/questions/7650448/django-serialize-queryset-values-into-json

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2016-11-21T23:35:33

The Old Way

import os

os.system('find /home/user/documents -type f -iname "*.doc"')

The New, Recommended Way

import subprocess

subprocess.check_call([
    'find',
    '/home/user/documents',
    '-type', 'f',
    '-iname', '*.doc'
])

Bonus Tidbit

At this point, we can incorporate some nice exception handling:

import subprocess

try:
    subprocess.check_call([
        'find',
        '/home ...

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2016-11-21T23:42:35
import logging

logging_config = {
    'filename': '/var/log/app_log',
    'format': '%(asctime)s [%(levelname)s] %(message)s',
    'level': logging.INFO
}
logging.basicConfig(**logging_config)

logging.info('Our logged message.')

This will output the following to /var/log/app_log:

2016-11-21 23:50:53,677 [INFO] Our logged message.

Source: https://docs.python.org/2/howto ...

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2017-12-29T16:14:00

It's easy to forget to update packages after they've been installed as they silently live in the background working as intended. Here are two ways to check what needs updating:

pip list --outdated 

Out of the box, pip provides a quick way to query which packages have updates.

pip-review

If ...

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2017-09-01T17:53:32

Here's the generalized snippet:

any(dict.get('key') == search_value for dict in list)

A full example:

authors = [
    {'author': 'Michael Crichton', title: 'Jurassic Park'},
    {'author': 'C.S. Lewis', title: 'Til We Have Faces'}
]

if any(book.get('author') == 'Michael Crichton' for book in books):
    print('Found Michael Crichton!')

Or less specifically ...

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2017-08-30T17:52:40

Using the ManifestStaticFilesStorage storage backend alters the filename of our static files. For example, style.css becomes something like style.3d94ea84cd8a.css. When collectstatic is run and finds a file that has changed, the MD5 portion of the filename will be updated (style.3d94ea84cd8a.css -> style.1d74ea7349df.css). This ...

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2017-08-27T08:56:34

Here's how I set up logging where:

  • Log files rotate nightly (at midnight).
  • We keep 10 total log files (as history).
import logging
import os

# Set up logging
logger = logging.getLogger(__file__)
handler_kwargs = {
    'filename': os.path.join(base_dir, 'file.log'),
    'when': 'midnight',
    'backupCount': 10
}
handler = handlers.TimedRotatingFileHandler(**handler_kwargs)
formatter = logging ...

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2017-08-27T08:44:20

Python 2.7 is not provided on CentOS 6 because Yum depends on Python 2.6. Simply installing 2.7 over 2.6 will break Yum. Thankfully, Red Hat provides us with an alternate installation method through their SCL project.

First, get Python 2.7 installed:
https://www.softwarecollections.org ...

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2017-08-24T07:47:57
# Simple List
', '.join([author.name for author in authors])

# Django
', '.join([author.name for author in book.author_set.all()])

Both will output "Author Name, Author 2 Name, ..., Author x Name"

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2017-08-24T21:01:28

Here's a custom manager for a class (Change) that gets all approved changes where "today's date" falls between the Change.start_date and Change.end_date.

# models.py
import datetime
...
# Custom Change Manager that only pulls active, approved changes
class ApprovedChanges(models.Manager):
    def get_queryset(self):
        today = datetime.date.today()
        return super ...

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2017-05-02T17:37:37

The following code allows us to monkey patch the json() method that is returned by requests.post().

import requests
from mock import MagicMock


@mock.patch.object(requests, 'post')
def my_function(self, post):
    attrs = {'json.return_value': {'id': 1}}
    post.return_value = MagicMock(**attrs)

    r = requests.post()
    r.json()['id']

Source: https://docs ...

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2017-05-29T10:58:45

I just started my first Django project with Python 3 in earnest. One of the first things I have noticed is that reload isn't available by default from the Django shell. It needs to be imported:

>>> from importlib import reload
>>> reload(<module>)

This became a pretty tedious process ...

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2017-04-03T20:16:40
from sqlalchemy.sql import text
from sqlalchemy import create_engine

import secrets


engine = create_engine(
    'mssql+pyodbc://{}:{}@MSSQL'.format(
        secrets.username, secrets.password
    )
)
conn = engine.connect()

s = text("SELECT * FROM users WHERE name = :name")
result = conn.execute(s, name=name).fetchall()
print result

For further information on installing and configuring unixODBC (requirement ...

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2017-02-16T15:41:13
#!/usr/bin/python
import sys


try: 
    hex_val = str(sys.argv[1])
except Exception as e:
    sys.exit('Please provide a hex code as an argument (e.g. hex2rgb 333333).')

r = int(hex_val[0:2], 16)
g = int(hex_val[2:4], 16)
b = int(hex_val[4:6], 16)

print('{}, {}, {}'.format(r ...

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