python snippets

dev_settings.py

"""
Template settings.py for django 1.4 projects during the developpement.
"""

import os

#store the asolute path of the file for future needs
self_absolute_path = os.path.abspath(__file__)
self_dir_absolute_path = os.path.dirname(self_absolute_path)
self_dir_name = os.path.split(self_dir_absolute_path)[1]

# Django settings for baseproject project.

DEBUG = True
TEMPLATE_DEBUG = DEBUG

ADMINS = (
    # ('Your Name', 'your_email@example.com'),
)

MANAGERS = ADMINS

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.', # Add 'postgresql_psycopg2', 'mysql', 'sqlite3' or 'oracle'.
        'NAME': self_dir_absolute_path+'/defaultdb.sqlite', # Or path to database file if using sqlite3.
        'USER': '', # Not used with sqlite3.
        'PASSWORD': '', # Not used with sqlite3.
        'HOST': '', # Set to empty string for localhost. Not used with sqlite3.
        'PORT': '', # Set to empty string for default. Not used with sqlite3.
    }
}

# Local time zone for this installation. Choices can be found here:
# http://en.wikipedia.org/wiki/List_of_tz_zones_by_name
# although not all choices may be available on all operating systems.
# In a Windows environment this must be set to your system time zone.
TIME_ZONE = 'America/Chicago'

# Language code for this installation. All choices can be found here:
# http://www.i18nguy.com/unicode/language-identifiers.html
LANGUAGE_CODE = 'en-us'

SITE_ID = 1

# If you set this to False, Django will make some optimizations so as not
# to load the internationalization machinery.
USE_I18N = True

# If you set this to False, Django will not format dates, numbers and
# calendars according to the current locale.
USE_L10N = True

# If you set this to False, Django will not use timezone-aware datetimes.
USE_TZ = True

# Absolute filesystem path to the directory that will hold user-uploaded files.
# Example: "/home/media/media.lawrence.com/media/"
MEDIA_ROOT = ''

# URL that handles the media served from MEDIA_ROOT. Make sure to use a
# trailing slash.
# Examples: "http://media.lawrence.com/media/", "http://example.com/media/"
MEDIA_URL = ''

# Absolute path to the directory static files should be collected to.
# Don't put anything in this directory yourself; store your static files
# in apps' "static/" subdirectories and in STATICFILES_DIRS.
# Example: "/home/media/media.lawrence.com/static/"
STATIC_ROOT = ''

# URL prefix for static files.
# Example: "http://media.lawrence.com/static/"
STATIC_URL = '/static/'

# Additional locations of static files
STATICFILES_DIRS = (
    # Put strings here, like "/home/html/static" or "C:/www/django/static".
    # Always use forward slashes, even on Windows.
    # Don't forget to use absolute paths, not relative paths.
)

# List of finder classes that know how to find static files in
# various locations.
STATICFILES_FINDERS = (
    'django.contrib.staticfiles.finders.FileSystemFinder',
    'django.contrib.staticfiles.finders.AppDirectoriesFinder',
# 'django.contrib.staticfiles.finders.DefaultStorageFinder',
)

# Make this unique, and don't share it with anybody.
SECRET_KEY = '+j49eo5x8-*yafuay(a!(3w+x^4z7t_+l)g3^eowj9m%zs7sb+'

# List of callables that know how to import templates from various sources.
TEMPLATE_LOADERS = (
    'django.template.loaders.filesystem.Loader',
    'django.template.loaders.app_directories.Loader',
# 'django.template.loaders.eggs.Loader',
)

MIDDLEWARE_CLASSES = (
    'django.middleware.common.CommonMiddleware',
    'django.contrib.sessions.middleware.SessionMiddleware',
    'django.middleware.csrf.CsrfViewMiddleware',
    'django.contrib.auth.middleware.AuthenticationMiddleware',
    'django.contrib.messages.middleware.MessageMiddleware',
    # Uncomment the next line for simple clickjacking protection:
    # 'django.middleware.clickjacking.XFrameOptionsMiddleware',
    'debug_toolbar.middleware.DebugToolbarMiddleware',
)

# set the urls module of the project assuming the settings file
# is placed in the main folder (the folder generated with the name
# of the project since django 1.4)
# of the project and the mail urls module is the one of this folder
ROOT_URLCONF = self_dir_name+'.urls'

# Python dotted path to the WSGI application used by Django's runserver.
WSGI_APPLICATION = self_dir_name+'.wsgi.application'

TEMPLATE_DIRS = (
    # Put strings here, like "/home/html/django_templates" or "C:/www/django/templates".
    # Always use forward slashes, even on Windows.
    # Don't forget to use absolute paths, not relative paths.
)

INSTALLED_APPS = (
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.sites',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    # Uncomment the next line to enable the admin:
    'django.contrib.admin',
    'debug_toolbar',
    # Uncomment the next line to enable admin documentation:
    # 'django.contrib.admindocs',
)

# A sample logging configuration. The only tangible logging
# performed by this configuration is to send an email to
# the site admins on every HTTP 500 error when DEBUG=False.
# See http://docs.djangoproject.com/en/dev/topics/logging for
# more details on how to customize your logging configuration.
LOGGING = {
    'version': 1,
    'disable_existing_loggers': False,
    'filters': {
        'require_debug_false': {
            '()': 'django.utils.log.RequireDebugFalse'
        }
    },
    'handlers': {
        'mail_admins': {
            'level': 'ERROR',
            'filters': ['require_debug_false'],
            'class': 'django.utils.log.AdminEmailHandler'
        }
    },
    'loggers': {
        'django.request': {
            'handlers': ['mail_admins'],
            'level': 'ERROR',
            'propagate': True,
        },
    }
}

INTERNAL_IPS = ('127.0.0.1',)

DEBUG_TOOLBAR_PANELS = (
    'debug_toolbar.panels.version.VersionDebugPanel',
    'debug_toolbar.panels.timer.TimerDebugPanel',
    'debug_toolbar.panels.settings_vars.SettingsVarsDebugPanel',
    'debug_toolbar.panels.headers.HeaderDebugPanel',
    'debug_toolbar.panels.request_vars.RequestVarsDebugPanel',
    'debug_toolbar.panels.template.TemplateDebugPanel',
    'debug_toolbar.panels.sql.SQLDebugPanel',
    'debug_toolbar.panels.signals.SignalDebugPanel',
    'debug_toolbar.panels.logger.LoggingPanel',
)


def custom_show_toolbar(request):
    return True # Always show toolbar, for example purposes only.

DEBUG_TOOLBAR_CONFIG = {
    'INTERCEPT_REDIRECTS': True,
    'SHOW_TOOLBAR_CALLBACK': custom_show_toolbar,
    'HIDE_DJANGO_SQL': False,
    'TAG': 'div',
    'ENABLE_STACKTRACES': True,
}

snippets.py

a = 5
b = 6
c = 7

print str(a)+' '+str(b)+' '+str(c)
# we can switch variables values without a temporary variable
a,b,c = b,c,a
print str(a)+' '+str(b)+' '+str(c)

def makedict(**kwargs):
# simplifies a bit the dictonnary declaration (mydict = {'foo':1, 'bar':2})
# to mydict = makedict(foo=1,bar=2)
    return kwargs

d = {'foo':1, 'bar':2}

if d.has_key('foo'):
    d['foo']
# is equivalent to
try:
    d['foo']
except KeyError:
    pass
# the better method:
d.get('foo') # return None if not found

# what may replace switch :

animals = []
number_of_felines = 0

def deal_with_a_cat( ):
    global number_of_felines
    print "meow"
    animals.append('feline')
    number_of_felines += 1

def deal_with_a_dog( ):
    print "bark"
    animals.append('canine')

def deal_with_a_bear( ):
    print "watch out for the *HUG*!"
    animals.append('ursine')

tokenDict = {
    "cat": deal_with_a_cat,
    "dog": deal_with_a_dog,
    "bear": deal_with_a_bear,
}

word = "cat"

functionToCall = tokenDict[word]
functionToCall()

# double comparison is possible
if 5 < 8 < 55:
    print "OK"

# a function may return more than one element (in fact a tuple is returned)
def f():
    return 1,2,3

res = f()
print res
a,b,c = f()
print str(a)+' '+str(b)+' '+str(c)

# function parameters/arguments

def myfunc(datas, opt_datas=[], *args, **kwargs):
    for d in datas: print(d)
    print "opt_datas"
    for d in opt_datas: print(d)
    print "args"
    for a in args:
        for d in a: print(d)
    print "kwargs"
    for v in kwargs.values():
        for d in v: print(d)

myfunc([1,2])
myfunc([1,2], [3,4])
myfunc([1,2], [3,4], [5,6])

myfunc(datas=[1,2])
myfunc(datas=[1,2], opt_datas=[3,4])
myfunc(datas=[1,2], opt_datas=[3,4], truc=[5,6])

# as the ternary operator in PHP
print(True and "OK" or "KO")
print(False and "OK" or "KO")

# list slices
a = range(11)
print a[:10]
print a[0:10]
print a[10:20] # looking for out of range indice doesn't raise exception
# starting from the end of the list
print a[-1]
print a[-10:]
print a[-10:-1]
# specify the step
print a[-10:-1:2]

# this set the same pointer on a and b:
b = a

# this copies a to b (b gets all the elements of a thanks to the slice)
b = a[:]

# slice and step may be used for loops
for c in a[11:0:-1]:
# equivalent to for index in range(11, 0, -1): print(a[index])
    print c

# you can cast tuple to list and list to tuple
ta = tuple(a)
b = list(ta)

# a way to build a dict
c = dict((k,v+5) for k,v in enumerate(a))
print c

# another way: generators

def gen(tab):
    for k,v in enumerate(tab):
        yield k, v+5

print dict((k,v) for k,v in gen(a))

# sorting list
a = [5,4,1,8,6,9]
print a
a.sort()
print a

# sorting list with defined comparison pattern
def comp(a, b):
    return cmp(-a,-b)

a.sort(comp)
print a

vcs_usage_since_2010.py

import matplotlib
matplotlib.use('Qt4Agg')
from matplotlib.pyplot import plot, xlim, ylim, show, legend, figure
import psycopg2
import datetime

# connecting to the database (replica on a virtual machine)
conn = psycopg2.connect(host='192.168.122.131', user='root', password='root', database='udd')
cursor = conn.cursor()

# querying the db to get timestamps of record after the first of jan. 2010
cursor.execute(
    "select ts,vcstype_git,vcstype_svn,vcstype_hg,vcstype_bzr, vcstype_arch, vcstype_cvs from history.sources_count where ts > '"+
        str(datetime.datetime(2010, 1, 1, 0, 0, 0))+"'")

# getting the results of the query
results = cursor.fetchall()

# setting the figure properties
figure(figsize=(8,6), dpi=80)

# storing ts and vcstype_git in axis vars
def datas_per_vcs(results):
    res = (('blue',[],'git'), ('green',[],'svn'),
            ('red',[],'hg'), ('yellow',[],'bzr'),
            ('black',[],'arch'),('brown',[],'cvs'))
    x = []
    for d in results:
        x.append(d[0])
        for k,v in enumerate(d):
            if 1 <= k <= 6:
                res[k-1][1].append(v)
    return res, x

def define_plot(color, data, label):
    plot(x, data, color=color, linewidth=1.0, linestyle='-', label=label)

datas_per_vcs, x = datas_per_vcs(results)

for d in datas_per_vcs:
    define_plot(d[0], d[1], d[2])

def get_max_y():
    max_y = max(datas_per_vcs[0][1])
    for d in datas_per_vcs:
        max_y = max(max_y, max(d[1]))

# setting the dimensions of the graph
xlim(min(x), max(x))
ylim(0, get_max_y())

legend(loc='upper left')

show()