A Few of My Favorite Things
Mike Pirnat • AG Interactive • CodeMash 2012

A Few of My Favorite Things
Mike Pirnat • AG Interactive • CodeMash 2012

Disclaimers

The Language

_ ( =
255,
lambda
V ,B,c
:c and Y(V*V+B,B, c
-1)if(abs(V)<6)else
( 2+c-4*abs(V)**-0.4)/i
) ;v, x=1500,1000;C=range(v*x
);import struct;P=struct.pack;M,
j ='<QIIHHHH',open('M.bmp','wb').write
for X in j('BM'+P(M,v*x*3+26,26,12,v,x,1,24))or C:
i ,Y=_;j(P('BBB',*(lambda T:(T*80+T**9
*i-950*T **99,T*70-880*T**18+701*
T **9 ,T*i**(1-T**45*2)))(sum(
[ Y(0,(A%3/3.+X%v+(X/v+
A/3/3.-x/2)/1j)*2.5
/x -2.7,i)**2 for
A in C
[:9]])
/9)
) )
http://preshing.com/20110926/high-resolution-mandelbrot-in-obfuscated-python

http://preshing.com/20110926/high-resolution-mandelbrot-in-obfuscated-python

The Interactive Shell
$ python
Python 2.7.1 (r271:86832, Jun 16 2011, 16:59:05)
[GCC 4.2.1 (Based on Apple Inc. build 5658) (LLVM build
2335.15.00)] on darwin
Type "help", "copyright", "credits" or "license" for
more information.
>>>

Docstrings...
class Frobulator(object):
"""It frobulates things."""
def __init__(self, doohickey):
"""A Frobulator needs a doohickey."""
self.doohickey = doohickey
def frobulate(self):
"""Frobulate ALL the things!"""
print "Frobulating..."
doodad = self.doohickey()
return FrobulatedThing(doodad)
class FrobulatedThing(object):
"""A thing which has been frobulated."""
def __init__(self, thing):
"""Make a thing into a frobulated thing."""
self.thing = thing

...and Help
>>> help(Frobulator)
Help on class Frobulator in module frobulator:
class Frobulator(__builtin__.object)
| It frobulates things.
|
| Methods defined here:
|
| __init__(self, doohickey)
| A Frobulator needs a doohickey.
|
| frobulate(self)
| Frobulate ALL the things!
|
...

Comprehensions
• List comprehensions
• Set comprehensions
• Dictionary comprehensions
• Generator expressions

List Comprehensions
x = [item for item in series]
x = [do_something(item) for item in series if expression]
things = [Thingy.from_data(x) for x in database_results]
partiers = [x for x in codemashers if x.slides_done()]

List Comprehensions
booze = ['beer', 'wine', 'scotch', 'gin']
soft_drinks = ['water', 'soda', 'juice']
a = [(x, y) for x in booze for y in soft_drinks]
[('beer', 'water'), ('beer', 'soda'), ('beer', 'juice'),
('wine', 'water'), ('wine', 'soda'), ('wine', 'juice'),
('scotch', 'water'), ('scotch', 'soda'), ('scotch',
'juice'), ('gin', 'water'), ('gin', 'soda'), ('gin',
'juice')]

List Comprehensions
b = [x for x in zip(booze, soft_drinks)]
[('beer', 'water'), ('wine', 'soda'), ('scotch', 'juice')]

Set Comprehensions
s = {v for v in 'CODEMASH ROCKS' if v not in 'ABCD'}
set([' ', 'E', 'H', 'K', 'M', 'O', 'S', 'R'])

Dictionary Comprehensions
d = {key: value for key, value in list_of_tuples}
d = {
'Mike': 'Python',
'Jim': 'Ruby',
'Brad': 'UX',
...
}
d1 = {val: key for key, val in d.items()}
{'Python': 'Mike', 'Ruby': 'Jim', 'UX': 'Brad', ...}

Generators
def f(how_many):
for number in range(how_many):
if number**2 > 3:
yield number * 2
for number in f(5):
print number
4
6
8

Generator Expressions
gen = (2*x for x in range(5) if x**2 > 3)
for number in gen:
print number
4
6
8

Properties
class Foo(object):
def __init__(self, bar=42):
self.set_bar(bar)
def get_bar(self):
return self.bar
def set_bar(self, bar):
self.bar = int(bar)

Properties
class Foo(object):
def __init__(self, bar=42):
self.bar = bar
@property
def bar(self):
return self._bar
@bar.setter
def bar(self, x):
self._bar = int(x)

Properties
class Foo(object):
def __init__(self, bar=42):
self.bar = bar
@property
def bar(self):
return self._bar
@bar.setter
def bar(self, x):
self._bar = int(x)

Properties
>>> foo = Foo()
>>> foo.bar
42
>>> foo.bar = 'abc'
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "<stdin>", line 9, in bar
ValueError: invalid literal for int() with base 10:
'abc'

Decorators
• That funny-looking @ thing
• Similar to Java’s annotations
• Replaces a function with a wrapper
• Augment functionality in a reusable way

Decorators
def be_excellent(wrapped):
def wrapper(*args, **kwargs):
print "Be excellent to each other..."
return wrapped(*args, **kwargs)
return wrapper
@be_excellent
def party_on(who):
print "...and party on, {0}!".format(who)
>>> party_on('dudes')
Be excellent to each other...
...and party on, dudes!

Context Managers
• That funny “with” thing
• Simplify calling code that needs setup and
teardown
• Alternative to try/finally structures
• Acquire locks, open and close files, do
database transactions, etc.

Before Context Managers
frobulator = Frobulator(...)
try:
frobulator.frobulate()
finally:
frobulator.cleanup()

After Context Managers
with Frobulator(...) as frobulator:
frobulator.frobulate()

class Frobulator(object):
def __init__(self, ...):
...
def __enter__(self):
print "Preparing to frobulate..."
return self
def __exit__(self, exc_type, exc_value, exc_tb):
print "Frobulation complete!"
def frobulate(self):
print "Frobulating!"
...

with Frobulator() as frobulator:
frobulator.frobulate()
Preparing to frobulate...
Frobulating!
Frobulation complete!

import contextlib
@contextlib.contextmanager
def make_frobulator():
print "Preparing to frobulate..."
yield Frobulator()
print "Frobulation complete!"
with make_frobulator() as frobulator:
frobulator.frobulate()
Preparing to frobulate...
Frobulating!
Frobulation complete!

The Standard Library

Itertools
• Tools for iterating on sequences
• Inspired by functional languages
• Fast and memory efficient
• Combine to express more complicated
algorithms

Itertools: chain
from itertools import chain
for x in chain([1, 2, 3], [42, 1138, 2112]):
print x,
1 2 3 42 1138 2112

Itertools: izip
from itertools import izip
for x in izip([1, 2, 3], [42, 1138, 2112]):
print x,
(1, 42) (2, 1138) (3, 2112)

Itertools: islice
from itertools import islice, count
for x in islice(count(), 5):
print x,
for x in islice(count(), 5, 10):
print x,
for x in islice(count(), 0, 100, 10):
print x,
0 1 2 3 4
5 6 7 8 9
0 10 20 30 40 50 60 70 80 90

Itertools: islice
from itertools import islice, count
for x in islice(count(), 5):
print x,
for x in islice(count(), 5, 10):
print x,
for x in islice(count(), 0, 100, 10):
print x,
0 1 2 3 4
5 6 7 8 9
0 10 20 30 40 50 60 70 80 90

Itertools: imap
from itertools import imap
for thingy in imap(Thingy.from_data, database_results):
...

Itertools: cycle
from itertools import cycle
for x in cycle(['wake up', 'meet Ned', 'romance Rita']):
print x
wake up
meet Ned
romance Rita
wake up
meet Ned
romance Rita
wake up
meet Ned
...

Itertools: repeat
from itertools import repeat
for x in repeat("stop hitting yourself", 5):
print x
stop hitting yourself
stop hitting yourself
stop hitting yourself
stop hitting yourself
stop hitting yourself

Functools
• Tools for manipulating functions
• Partial
• Wraps a callable with default arguments
• Alternative to lambdas and closures

Functools: Partial
from functools import partial
def f(a, b=2):
print a, b
f1 = partial(f, 'fixed_a')
f2 = partial(f, b='fixed_b')
>>> f1(b=1138)
fixed_a 1138
>>> f2(1138)
1138 fixed_b

Functools: Partial
def category_is(category, item):
categories = [x.lower() for x in item.categories]
if category.lower() in categories:
return True
return False
is_python = partial(category_is, 'python')
is_cat_pictures = partial(category_is, 'catpix')
...
python_posts = [item for item in blog_posts if is_python(item)]
cat_posts = [item for item in blog_posts if is_cat_pictures(item)]

Collections
• Beyond the basic list, dict, tuple, and set...
• Counter
• Defaultdict
• OrderedDict
• Namedtuple
• ...and more

Counter
counter = {}
for char in "Hello there, CodeMash!":
if char not in counter:
counter[char] = 1
else:
counter[char] += 1
print counter
{'a': 1, ' ': 2, 'C': 1, 'e': 4, 'd': 1, 'H': 1, 'M': 1,
'l': 2, 'o': 2, ',': 1, 's': 1, 'r': 1, '!': 1, 't': 1,
'h': 2}

Counter
counter = {}
for char in "Hello there, CodeMash!":
if char not in counter:
counter[char] = 1
else:
counter[char] += 1
print counter
{'a': 1, ' ': 2, 'C': 1, 'e': 4, 'd': 1, 'H': 1, 'M': 1,
'l': 2, 'o': 2, ',': 1, 's': 1, 'r': 1, '!': 1, 't': 1,
'h': 2}

Counter
from collections import Counter
counter = Counter("Hello there, CodeMash!")
print counter
Counter({'e': 4, ' ': 2, 'l': 2, 'o': 2, 'h': 2, 'a': 1,
'C': 1, 'd': 1, 'H': 1, 'M': 1, ',': 1, 's': 1, 'r': 1,
'!': 1, 't': 1})

Counter
from collections import Counter
counter = Counter("Hello there, CodeMash!")
print counter
Counter({'e': 4, ' ': 2, 'l': 2, 'o': 2, 'h': 2, 'a': 1,
'C': 1, 'd': 1, 'H': 1, 'M': 1, ',': 1, 's': 1, 'r': 1,
'!': 1, 't': 1})

Namedtuple
import math
def distance(a, b):
return math.sqrt(
(a[0] - b[0])**2 +
(a[1] - b[1])**2 +
(a[2] - b[2])**2
)
a = (1, 2, 3)
b = (-1, -2, 42)
print distance(a, b)
39.25557285278104

Namedtuple
from collections import namedtuple
Point = namedtuple('Point', 'x y z')
def distance(a, b):
return math.sqrt(
(a.x - b.x)**2 +
(a.y - b.y)**2 +
(a.z - b.z)**2
)
a = Point(x=1, y=2, z=3)
b = Point(-1, -2, 42)
print distance(a, b)
39.25557285278104

Difflib
s1 = """
Lorem ipsum dolor sit amet, consectetur adipiscing elit.
Phasellus dui nunc, faucibus id ullamcorper eget, tempus
vitae nisl. Donec quis semper risus. Curabitur sit amet
tellus eget metus accumsan porta nec nec lorem. Ut vitae
sem nisl. Praesent pulvinar feugiat nibh fringilla
semper. Nullam cursus tempor lorem ut egestas. Nullam
suscipit gravida turpis ac porttitor. Curabitur eleifend
augue at risus commodo pretium. Aliquam eget magna
risus, ut lobortis metus. Cum sociis natoque penatibus
et magnis dis parturient montes, nascetur ridiculus mus.
Etiam non magna sit amet nulla porttitor molestie sit
amet vel sem. Vestibulum sit amet nisl a velit
adipiscing porta id non urna. Duis ullamcorper dictum
ipsum sit amet congue.
"""

Difflib
s2 = """
Lorem ipsum dolor sit amet, consectetur adipiscing elit.
Phasellus dui nunc, faucibus id ullamcorper eget, tempus
vitae nisl. Donec quis semper risus. Curabitur sit amet
tellus eget metus accumsan porta nec nec lorem. Ut vitae
sem nisl. Praesent pulvinar feugiat nibh fringilla
semper. Nullam cursus tempor lorem ut egestas. Nullam
suscipit gravida turpis ac porttitor. Curabitur eleifend
augue at risus commodo pretium. Aliquam eget magna
risus, ut lobortis montes. Cum sociis natoque penatibus
et magnis dis parturient metus, nascetur ridiculus mus.
Etiam non magna sit amet nulla porttitor molestie sit
amet vel sem. Vestibulum sit amet nisl a velit
adipiscing porta id non urna. Duis ullamcorper dictum
ipsum sit amet congue.
"""

Difflib
import difflib
differ = difflib.Differ()
diff = differ.compare(s1.splitlines(), s2.splitlines())
print 'n'.join(diff)

Difflib
Lorem ipsum dolor sit amet, consectetur adipiscing elit.
Phasellus dui nunc, faucibus id ullamcorper eget, tempus
vitae nisl. Donec quis semper risus. Curabitur sit amet
tellus eget metus accumsan porta nec nec lorem. Ut vitae
sem nisl. Praesent pulvinar feugiat nibh fringilla
semper. Nullam cursus tempor lorem ut egestas. Nullam
suscipit gravida turpis ac porttitor. Curabitur eleifend
augue at risus commodo pretium. Aliquam eget magna
- risus, ut lobortis metus. Cum sociis natoque penatibus
? --
+ risus, ut lobortis montes. Cum sociis natoque penatibus
? +++
- et magnis dis parturient montes, nascetur ridiculus mus.
? ^^ ^
+ et magnis dis parturient metus, nascetur ridiculus mus.
? ^ ^
Etiam non magna sit amet nulla porttitor molestie sit
amet vel sem. Vestibulum sit amet nisl a velit
adipiscing porta id non urna. Duis ullamcorper dictum
ipsum sit amet congue.

Difflib
diff = difflib.unified_diff(
s1.splitlines(), s2.splitlines(), lineterm='')
print 'n'.join(diff)

Difflib
---
+++
@@ -7,8 +7,8 @@
semper. Nullam cursus tempor lorem ut egestas. Nullam
suscipit gravida turpis ac porttitor. Curabitur eleifend
augue at risus commodo pretium. Aliquam eget magna
-risus, ut lobortis metus. Cum sociis natoque penatibus
-et magnis dis parturient montes, nascetur ridiculus mus.
+risus, ut lobortis montes. Cum sociis natoque penatibus
+et magnis dis parturient metus, nascetur ridiculus mus.
Etiam non magna sit amet nulla porttitor molestie sit
amet vel sem. Vestibulum sit amet nisl a velit
adipiscing porta id non urna. Duis ullamcorper dictum

Ast
• Use Python to process abstract syntax trees
of Python grammar
• Helps introspect about what the current
grammar looks like
• Helps write secure code

Ast
# Danger:
foo = eval(bar)
# Safe:
foo = ast.literal_eval(bar)

Multiprocessing
• Like threading, but with subprocesses
• Local and remote concurrency
• Spawn processes or entire pools
• Communicate via queues or pipes
• Shared state via shared memory or
manager/server process

import os
from multiprocessing import Process
def info(title):
print title
print 'parent process:', os.getppid()
print 'process id:', os.getpid()
def f(name):
info('function f')
print 'hello', name
if __name__ == '__main__':
info('main')
p = Process(target=f, args=('world',))
p.start()
p.join()

$ python process.py
main
parent process: 18647
process id: 31317
----------
function f
parent process: 31317
process id: 31318
----------
hello world

import os
from multiprocessing import Pool
def g(x):
info('function g('+str(x)+')')
return x * x
if __name__ == '__main__':
info('main')
pool = Pool(2)
print pool.map(g, range(100))

$ python process.py parent process: 31369
main parent process: 31369
module name: __main__ process id: 31370
parent process: 18647 process id: 31371
process id: 31369 ----------
---------- ----------
function g(0) function g(4)
module name: __main__ module name: __main__
parent process: 31369 parent process: 31369
process id: 31370 function g(14)
---------- process id: 31370
function g(1) module name: __main__
module name: __main__ ----------
parent process: 31369 parent process: 31369
process id: 31370 function g(5)
---------- process id: 31371
function g(13) module name: __main__
function g(2)
module name: __main__ ...
parent process: 31369
process id: 31370 [0, 1, 4, 9, 16, 25, ..., 8836,
---------- 9025, 9216, 9409, 9604, 9801]
module name: __main__
function g(3)
module name: __main__

Third Party Packages

Third Party Packages
• Most available on PyPI--http://pypi.python.org
• pip install packagename
• easy_install packagename

Virtualenv
• Makes an isolated Python environment
• Don’t pollute your global site-packages
• Insulates Python projects from one another
• Don't have to be root

Virtualenv
$ virtualenv directory
$ virtualenv --python=/path/to/specific/python directory
$ cd directory
$ . bin/activate
$ easy_install whatever
$ pip install whatever
...do stuff...
$ deactivate

Datetime and Dateutil
• Python’s datetime provides date, time,
datetime, and timedelta objects
• Dateutil provides powerful extensions
• Parsing
• Olson-driven timezones
• Recurrence

Parsing
>>> from dateutil.parser import parse
>>> parse('01/01/2012')
datetime.datetime(2012, 1, 1, 0, 0)
>>> parse('2012-01-01')
datetime.datetime(2012, 1, 1, 0, 0)

Timezones
>>> from dateutil import zoneinfo
>>> zone = zoneinfo.gettz('US/Eastern')
>>> zone
tzfile('America/New_York')
>>> zone2 = zoneinfo.gettz('US/Hawaii')
>>> dt = datetime.now(zone)
>>> dt
datetime.datetime(2012, 1, 13, 13, 46, 54, 997825,
tzinfo=tzfile('America/New_York'))
>>> dt.astimezone(zone2)
datetime.datetime(2012, 1, 13, 8, 46, 54, 997825,
tzinfo=tzfile('Pacific/Honolulu'))

Recurrence
>>> from dateutil.rrule import rrule, YEARLY, MONTHLY,
WEEKLY, DAILY, HOURLY, MINUTELY, SECONDLY, BY_EASTER
>>> rr = rrule(YEARLY, dtstart=datetime(1948, 2, 24))
>>> rr.after(datetime(2012, 1, 1))
datetime(2012, 2, 24, 0, 0)
>>> rr.between(datetime(2010, 1, 1),
datetime(2012, 1, 1))
[datetime(2010, 2, 24, 0, 0),
datetime(2011, 2, 24, 0, 0)]

howoldismykid.com
def periods_between(freq, start_date, end_date):
# dateutil.rrule falls down for monthly recurrences where the start
# date's day is greater than the number of days in a subsequent month
# in the range; ie, when start date is 10/31/2010, and end date is
# 3/13/2011, rrule's between will only produce 2 instances, 12/31 and
# 1/31, rather than 4.
if freq == MONTHLY and start_date.day > 28:
start_date = datetime.datetime(start_date.year, start_date.month,
28, start_date.hour, start_date.minute, start_date.second)
# Same problem but for "Pirates of Penzance" leap day birthdays...
elif freq == YEARLY and is_leap_day(start_date):
start_date = datetime.datetime(start_date.year, start_date.month,
28, start_date.hour, start_date.minute, start_date.second)
rr = rrule(freq, dtstart=start_date)
periods = len(rr.between(start_date, end_date))
return periods

howoldismykid.com
>>> start_date = datetime(2007, 9, 10)
>>> end_date = datetime(2012, 1, 13)
>>> periods_between(YEARLY, start_date, end_date)
4
>>> periods_between(MONTHLY, start_date, end_date)
52
>>> periods_between(WEEKLY, start_date, end_date)
226
>>> periods_between(DAILY, start_date, end_date)
1585

Nose
• Find, run, and report results of test suites
• Low-friction setup
• Extendable with plugins (more later)
• http://readthedocs.org/docs/nose/en/latest/

Nose
# test_foo.py
def test_a_thing():
assert False
def test_another_thing():
assert True

Nose
$ nosetests tests/test_foo.py
F.
======================================================================
FAIL: test_foo.test_a_thing
----------------------------------------------------------------------
Traceback (most recent call last):
File "/Users/mpirnat/Code/frobulator/lib/python2.7/site-packages/
nose-1.1.2-py2.7.egg/nose/case.py", line 197, in runTest
self.test(*self.arg)
File "/Users/mpirnat/Code/frobulator/src/frobulator/tests/test_foo.py",
line 2, in test_a_thing
assert False
AssertionError
----------------------------------------------------------------------
Ran 2 tests in 0.001s
FAILED (failures=1)

Nose
class TestWhenFrobulating(object):
def setup(self):
self.frobulator = Frobulator()
self.frobulator.frobulate()
def test_that_it_frobulated(self):
assert self.frobulator.has_frobulated
def teardown(self):
self.frobulator.cleanup()

Nose
$ nosetests
.
--------------------------------------------------------
Ran 1 test in 0.005s
OK

Nose: Useful Flags
• --processes=number
• -x
• --pdb
• --pdb-failures
• --failed

Nose Plugins
• Add custom behavior to your test run
• Get coverage statistics (coverage)
• Measure cleanliness with PEP-8 (tissue)
• Emit human-readable spec-style results
(pinocchio)
• Or write your own...

class TestGeneratesLotsOfFailures(object):
def test_generates_failures(self):
def _make_a_test(i):
# start with some wins
if i < 7:
assert True
# but then it hits the fan...
elif i < 30:
assert False
# then be a little random
elif i % 3 == 0:
assert False
else:
assert True
for i in range(50):
yield _make_a_test, i

$ nosetests test_epic_fail.py
.......FFFFFFFFFFFFFFFFFFFFFFFF..F..F..F..F..F..F.
[lots of test failure output; use your imagination...]
--------------------------------------------------------
Ran 50 tests in 0.010s
FAILED (errors=30)

import os
from nose.plugins import Plugin
class F7U12(Plugin):
name = 'f7u12'
enabled = True
def options(self, parser, env=os.environ):
super(F7U12, self).options(parser, env=env)
def configure(self, options, config):
super(F7U12, self).configure(options, config)
self.config = config
if not self.enabled:
return

def setOutputStream(self, stream):
self.stream = stream
return self.stream
def begin(self):
self.failure_count = 0
def handleFailure(self, test, err):
self.failure_count += 1
if self.failure_count < 8:
self.stream.write('F')
else:
self.stream.write('U')
return True

$ nosetests --with-f7u12 test_epic_fail.py
.......FFFFFFFFUUUUUUUUUUUUUUUU..U..U..U..U..U..U.
[lots of test failure output; use your imagination...]
--------------------------------------------------------
Ran 50 tests in 0.010s
FAILED (errors=30)

Mock
• Mock object framework
• Avoid writing custom stubs
• Uses “Action/Assert” model (not “Record/
Replay”)
• Can also patch out module and class
attributes in the scope of a test
• http://www.voidspace.org.uk/python/mock/

Mock
from mock import Mock
foo = Mock()
foo.bar()
foo.bar.baz(42)
foo.bar.baz.return_value = "whatever"
assert foo.bar.called
foo.bar.baz.assert_called_with(42)

Mock
class TestWhenFrobulating(object):
def setup(self):
self.doohickey = Mock()
self.frobulator = Frobulator(self.doohickey)
self.frobulator.frobulate()
def test_it_uses_the_doohickey(self):
assert self.doohickey.called

Mock
from mock import patch
class TestWhenFrobulating(object):
@patch('frobulator.DingleHopper')
def setup(self, dingle_hopper_class):
self.dingle_hopper = Mock()
dingle_hopper_class.return_value =
self.dingle_hopper
self.frobulator = Frobulator()
self.frobulator.frobulate()
def test_it_uses_a_dingle_hopper(self):
assert self.dingle_hopper.called

Coverage
• Measure coverage of your codebase during
program execution
• Integrates with several test runners to
measure test coverage
• http://nedbatchelder.com/code/coverage/

#!/usr/bin/env python
class Frobulator(object):
"""It frobulates things."""
def __init__(self, doohickey):
"""A Frobulator needs a doohickey."""
self.doohickey = doohickey
def frobulate(self):
"""Frobulate ALL the things!"""
print "Frobulating..."
doodad = self.doohickey()
return FrobulatedThing(doodad)
class FrobulatedThing(object):
"""A thing which has been frobulated."""
def __init__(self, thing):
"""Make a thing into a frobulated thing."""
self.thing = thing
if __name__ == '__main__':
x = FrobulatedThing(42)

#!/usr/bin/env python
class Frobulator(object):
"""It frobulates things."""
def __init__(self, doohickey):
"""A Frobulator needs a doohickey."""
self.doohickey = doohickey
def frobulate(self):
"""Frobulate ALL the things!"""
print "Frobulating..."
doodad = self.doohickey()
return FrobulatedThing(doodad)
class FrobulatedThing(object):
"""A thing which has been frobulated."""
def __init__(self, thing):
"""Make a thing into a frobulated thing."""
self.thing = thing
if __name__ == '__main__':
x = FrobulatedThing(42)

$ coverage run frobulator.py
$ coverage report -m
Name Stmts Miss Cover Missing
------------------------------------------
frobulator 12 4 67% 8, 12-14

from mock import Mock, patch
from frobulator import Frobulator, FrobulatedThing
class TestWhenFrobulating(object):
def setup(self):
self.doohickey = Mock()
self.doohickey.return_value = 42
self.frobulator = Frobulator(self.doohickey)
self.result = self.frobulator.frobulate()
def test_it_uses_a_doohickey(self):
assert self.doohickey.called
def test_it_returns_a_frobulated_thing(self):
assert isinstance(self.result, FrobulatedThing)

$ nosetests --with-coverage --cover-package frobulator
..
Name Stmts Miss Cover Missing
------------------------------------------
frobulator 12 1 92% 26
------------------------------------------
Ran 2 tests in 0.008s
OK

Useful Flags
• --cover-erase
• --cover-inclusive
• --cover-tests

Lettuce
• Like Cucumber
• BDD test framework
• Natural language augmented by code
• Big wins pairing Devs + QA + Biz
• http://lettuce.it/

Lettuce Vocabulary
• Features
• Scenarios
• Steps
• World
• Terrain

Feature: The website has a homepage
In order to demo Lettuce
As a presenter
I want to test the homepage of a website
Scenario: Verify the site is up
Given I access the url "http://localhost:8000/"
Then I get a status "200"

from lettuce import step, world
from nose.tools import assert_equals
import requests
@step(r'I access the url "(.*)"')
def access_url(step, url):
world.response = requests.get(url)
@step(r'I get a status "(.*)"')
def get_status(step, expected_status):
expected_status = int(expected_status)
assert_equals(world.response.status_code,
expected_status)

Snake-Guice
• Framework for Dependency Injection
• Reduce coupling!
• Improve testability!
• http://code.google.com/p/snake-guice/

Snake-Guice
• Bind identifiers to things you want to inject
• Decorate code with injection hints
• Use injector to get instance with all
dependencies resolved and injected
• Construct with mocks in tests, minimize the
need for patching

Define the Identifier
class IFrobulator(object):
pass

Decorate Your Code
from snakeguice import inject
class WankelRotator(object):
@inject(frobulator=IFrobulator)
def __init__(self, frobulator):
self.frobulator = frobulator

Decorate Your Code
from snakeguice import inject
class WankelRotator(object):
@inject(frobulator=IFrobulator)
def __init__(self, frobulator):
self.frobulator = frobulator

Configure Bindings
from frobulator import Frobulator
class BindingModule(object):
def configure(self, binder):
binder.bind(IFrobulator, to=Frobulator)

Get an Instance
from snakeguice import Injector
import WankelRotator
injector = Injector(BindingModule())
rotator = injector.get_instance(WankelRotator)

Requests
• A human-friendly alternative to urllib2
• Maturing rapidly
• http://python-requests.org/

Using Requests
import requests
# Authentication!
r = requests.get('https://api.github.com',
auth=('user', 'pass'))
print r.status_code
print r.headers['content-type']

Using Requests
# Posting name-value pair form data
post_data = {'foo': 'bar', 'baz': 'quux', ...}
r = requests.post(url, data=post_data)
# Posting a glob of JSON
r = requests.post(url, data=json.dumps(post_data))
# Multipart file attachment
files = {'my_file.xls': open('my_file.xls', 'rb')}
r = requests.post(url, files=files)

Using Requests
# Custom headers!
headers = {'X-foo': 'bar'}
r = requests.get(url, headers=headers)
# Cookies!
cookies = {'a_cookie': 'is delicious'}
r = requests.get(url, cookies=cookies)

Pylons
• http://docs.pylonsproject.org/en/latest/docs/
pylons.html
• MVCish web framework
• Glues together several component projects
• Can use your preferred components
• Somewhat dead (evolved into Pyramid)

Pylons
• Request/response: webob
• URL dispatch: routes
• Input validation: formencode
• Persistence/ORM: sqlalchemy
• Session: beaker
• Templates: mako

from routes import Mapper
def make_map(config):
"""Create, configure and return the routes Mapper"""
map = Mapper(directory=config['pylons.paths']['controllers'],
always_scan=config['debug'])
...
map.connect('/', controller='main', action='index')
map.connect('/contact', controller='contact', action='index',
conditions={'method':'GET'})
map.connect('/contact', controller='contact', action='send',
conditions={'method':'POST'})
return map

from howoldismykid.lib.base import BaseController,
render
class MainController(BaseController):
def index(self):
# Return a rendered template
return render('/main.mako')

from formencode import Schema, validators
class ContactForm(Schema):
email = validators.Email(not_empty=True)
subject = validators.String(not_empty=True)
message = validators.String(not_empty=True)

from pylons.decorators import validate
from howoldismykid.lib.base import BaseController, render
from howoldismykid.model.forms import ContactForm
class ContactController(BaseController):
def __init__(self, *args, **kwargs):
BaseController.__init__(self, *args, **kwargs)
self.emailer = Emailer(SMTP, USER, PW, FAKE_EMAIL)
def index(self):
# Return a rendered template
return render('/contact.mako')
@validate(schema=ContactForm(), form="index", prefix_error=False)
def send(self):
validated = self.form_result
self.emailer.send_mail(validated['email'], EMAIL,
validated['subject'], validated['message'])
return render('/contact_done.mako')

<!DOCTYPE HTML>
<html>
<head>
${self.head_tags()}
...
</head>
<body>
<div id="header">...</div>
<div id="content">
${self.body()}
</div>
<div id="footer">...</div>
<%include file="google_analytics.mako"/>
${self.foot_tags()}
</body>
</html>

<%inherit file="/base.mako" />
<%def name="head_tags()">
<title>How Old Is My Kid?</title>
</%def>
<h2>Contact Us</h2>
<p>Suggest a new feature, let us know how we're doing, or just say hi.</p>
<form method="POST" action="/contact" id="contact-form">
<p><label for="email">Email:</label> <input type="text" name="email"
id="email" /></p>
<p><label for="subject">Subject:</label> <input type="text"
name="subject" id="subject" /></p>
<p><label for="message">Message:</label><br />
<textarea name="message" id="message"></textarea></p>
<p><input type="submit" value="Submit" /></p>
</form>
<%def name="foot_tags()">
<script type="text/javascript">
$(document).ready(function() {
$("button, input:submit").button();
});
</script>
</%def>

Django
• https://www.djangoproject.com/
• Full stack/harder to replace components
• Lots of reusable apps
• Admin interface
• Lots of deployment options (Google)
• Not dead

from django.conf.urls.defaults import patterns, url
urlpatterns = patterns('',
url(r'^/$', 'howoldismykid.views.main',
name='main'),
url(r'^/contact/$', 'howoldismykid.views.contact',
name='contact'),
)

from django.shortcuts import render
def main(request):
return render(request, 'main.html')

from django import forms
class ContactForm(forms.Form):
email = forms.EmailField(label='Email Address')
subject = forms.CharField(label='Subject')
message = forms.CharField(label='Message',
widget=forms.Textarea)

from contact.forms import ContactForm
from django.shortcuts import render
def contact(request):
if request.method == 'POST':
form = ContactForm(request.POST)
if form.is_valid():
emailer =
Emailer(SMTP, USER, PW, FAKE_EMAIL)
emailer.send_mail(
form.cleaned_data['email'], EMAIL,
form.cleaned_data['subject'],
form.cleaned_data['message'])
return render(request, 'contact_done.html')
else:
form = ContactForm()
return render(request, 'contact.html',
{'form': form })

<!DOCTYPE HTML>
<html>
<head>
{% block head_tags %}...{% endblock %}
...
</head>
<body>
<div id="header">...</header>
<div id="content">
{% block content %}It goes here.{% endblock %}
</div>
<div id="footer">...</div>
{% include "google_analytics.html" %}
{% block foot_tags %}{% endblock %}
</body>
</html>

{% extends 'base.html' %}
{% block head_tags %}
<title>How Old Is My Kid?</title>
{% endblock %}
{% block content %}
<h2>Contact Us</h2>
<p>Suggest a new feature, let us know how we're doing, or just say hi.</p>
<form method="POST" action="/contact" id="contact-form">
{% csrf_token %}
{{ form.as_p }}
<p><input type="submit" value="Submit" /></p>
</form>
{% endblock %}
{% block foot_tags %}
<script type="text/javascript">
$(document).ready(function() {
$("button, input:submit").button();
});
</script>
{% endblock %}

The Culture

Planet Python
• http://planet.python.org/
• Aggregate feed of Python blogs
• Great way to follow what's going on
• Minimize newsgroup/mailing list burdens
• Easy to be included

The Python Ecosystem
• http://mirnazim.org/writings/python-
ecosystem-introduction/
• Great introduction to the Python ecosystem
• Everything you need to get up and running

The Hitchhiker’s Guide
• http://docs.python-guide.org/
• Opinionated advice about using Python
• Basics
• Scenario-specific details and
recommendations

PyMotW
• Explored a different standard library module
every week
• Examples, examples, examples
• http://www.doughellmann.com/PyMOTW/
• The Python Standard Library by Example
http://www.doughellmann.com/books/byexample/

Podcasts
• http://www.radiofreepython.com/
• http://frompythonimportpodcast.com/
• http://djangodose.com/
• http://advocacy.python.org/podcasts/
• http://www.awaretek.com/python/
• Start your own! Be the change you want...

PyOhio
• Free as in $0.00
• Columbus, Ohio
• Last weekend in July
• http://pyohio.org

PyCon
• Great people
• Great vibe
• All volunteer–personal ownership
• Video! http://pycon.blip.tv/
• 2012 & 2013: Santa Clara
• 2014 & 2015: Montreal

TiP BoF
• Testing in Python Birds of a Feather
• Lightning Talks
• Heckling...

...and goats

The Zen
• Guiding principles
• Sage advice
• >>> import this

The Zen
• Beautiful is better than ugly. • Readability counts.
• Explicit is better than • Special cases aren't special
implicit. enough to break the rules.
• Simple is better than • Although practicality beats
complex. purity.
• Complex is better than • Errors should never pass
complicated. silently.
• Flat is better than nested. • Unless explicitly silenced.
• Sparse is better than dense.

The Zen
• In the face of ambiguity, • Although never is often
refuse the temptation to better than right now.
guess.
• If the implementation is
• There should be one– hard to explain, it's a bad
and preferably only one– idea.
obvious way to do it.
• If the implementation is
• Although that way may not easy to explain, it may be a
be obvious at first unless good idea.
you're Dutch.
• Namespaces are one
• Now is better than never. honking great idea -- let's
do more of those!

What About You?

Fin
• Twitter: @mpirnat
• Blog: http://mike.pirnat.com
• Win a special prize–name all the movies
• Thanks for coming!