kyle-eshares

class conduit(object):
    def __init__(self, iterator):
        self.iterator = iterator

    def filter(self, predicate):
        return conduit(itertools.ifilter(predicate, self.iterator))

    def map(self, func):
        return conduit(itertools.imap(func, self.iterator))

kyle-eshares

from django.db import connection

def flatten(*args):
    def transform_pipeline(mdl):
        data = FlatData()
        num_before = len(connection.queries)
        for fn in args:
            fn(data, mdl)
        assert len(connection.queries) == num_before
        return data

kyle-eshares

# computations.py

def add_shareholder_name(shareholder_ix):
    def inner(flat, mdl):
        flat.shareholder_name = shareholder_ix[mdl.shareholder_id]
    return inner

def add_transfered_to_labels(transfered_to_ix):
    def inner(flat, mdl):
        flat.exercised_from_labels = [

kyle-eshares

def is_canceled(report_date)
    def inner(flat, mdl):
        flat.is_canceled = mdl.canceled_date < report_date
    return inner

report_date = datetime.today()

flat_securities = (
  conduit(all_securities)
      .map(

kyle-eshares

Author
------
authors.id | authors.name
-------------------
1         |  "paul"
2         |  "peter"
3         |  "john"

Books
-----

kyle-eshares

>> id(author)
4504693520
>>> [(id(book.author), book.author.pk) for book in author.books.all()]
[(4504693520, 1), (4504693520, 1)]

kyle-eshares

#  Don't waste a query if you are using the queryset
books = Book.objects.filter(..)
if len(books) > 5:
  do_stuff_with_books(books)

#  If you aren't using the queryset use count
books = Book.objects.filter(..)
if books.count() > 5:
  do_some_stuff()

kyle-eshares

#  Don't waste a query if you are using the queryset
books = Book.objects.filter(..)
if books:
  do_stuff_with_books(books)

#  If you aren't using the queryset use exist
books = Book.objects.filter(..)
if books.exists():
  do_some_stuff()

kyle-eshares

def author_name_length(book):
    return len(book.author.name)


def process_author_books(author):
    for book in author.books.all():
        do_stuff(book)

kyle-eshares

# Get the Author's name of a Book
book = Book.objects.first()
book.author.name