Django/Python Notes

using_djan

1. django-admin.py startproject <mysite>
	creates folder <mysite>
		with:
			manage.py: A command-line utility that lets you interact with this 					Django project in various ways.
			mysite/: actual python package for the project
				__init__.py: An empty file that tells Python that this 						directory should be considered a Python package.
				settings.py: Settings/configuration for this Django 						project
				urls.py: The URL declarations for this Django project; a 					“table of contents” of your Django-powered site.
				wsgi.py: An entry-point for WSGI-compatible web servers to 					serve your project. 

2. test server from cd <mysite> 
	$ python manage.py runserver

create app: 
	$ python manage.py startapp <app name>

tell project that app is installed : add <app name> to INSTALLED_APPS in settings.py

run to see CREATE TABLE OUTPUT (does not actually run database)
	$ python manage.py sql polls

check for errors in the model
	$ pythong manage.py validate

output any custom (if applicable) SQL statements such as table modifications
or constraints define for the application

* create the model tables in the database
	@ python manage.py syncdb

* invoke the shell for python
	$ python manage.py shell

start the development server
	$ python manage.py runserver

Views

open the <app_name>/views.py and write:
	def index(request):
	    return HttpResponse("")
to call the view, map it to a URL using URLconf

import conventions:
import numpy as np
import pandas as pd
import matplotlib.pyplot as plt

ex: np.arange
do not (from <above_libs> import *) #because these are too large of packages

munge/munging/wrangling: manipulating unstructured data into clean data

import json
path = ""
#expression is called list comprehension. applying the json.loads operation to collection
records = [json.loads(line) for line in open(path)]

#extracting all the timezone fields, checking to see if it exist first
time_zones = [rec['tz'] for rec in records if 'tz' in rec]

#counting the time_zones using std lib in Py
def get_counts(sequence):
    counts = {}
    for x in sequence:
	if x in counts:
	    counts[x] += 1
	else:
	    counts[x] = 1
	return counts

#using pandas data structure; DataFrame
from pandas import DataFrame, Series
import pandas as pd; import numpy as np
frame = DataFrame(records)
#call it to get the summary view
frame
#return the Series
frame['tz'][:10]
#use the Series object method: value_counts
tz_counts = frame['tz'].value_counts()
tz_counts[:10]

#the fillna function can replace missing values
clean_tz = frame['tz'].fillna('Missing')
clean_tz[clean_tz == ''] = 'Unknown'
tz_counts = clean_tz.value_counts()
tz_counts[:10]

#use the matplotlib to plot
tz_counts[:10].plot(kind='barh' rot=0)

#parsing the Series results to get agent 
#ex:
frame['a'][50]
u'Mozilla/5.0 (Windows NT 5.1; rv:10.0.2) Gecko/20100101 Firefox/10.0.2'

results = Series([x.split()[0] for x in frame.a.dropna()])
results[:5]
#prints just agent/browser and version

#close but not equal to one for floating point sums
np.allclose(<object>.groupby(['<>','<>']).prop.sum(), 1)