CIS 192 Week 5: Modules, Scripting, TestingCIS 192 Week 5: Modules, Scripting, Testing

Material adapted from Jorge Mendez

AnnouncementsAnnouncements

HW 2 due tomorrow at 11:59pmno class or assignments due next weekHW 3 out today, due in two weeks on 10/16

more moving parts, start early!

Where we are headedWhere we are headed

modulesscrip�ngtes�ng

Scripting as we know itScripting as we know it

.py filesexecuted by running python3 script.py

Example: Example: generator.py as basic script as basic script

ModulesModules

when wri�ng a .py file, we are also crea�ng a

contains func�on and class defini�onscan be imported into other modulesaccess the name of the current module with __name__

module(h�ps://docs.python.org/3/tutorial/modules.html)

https://docs.python.org/3/tutorial/modules.html

ModulesModules

may contain executable statements along with defini�onsthese statements are run upon impor�ng the module

modules define a namespaceglobal variables live within the moduleaccess them from outside the module via module_name.attr

Importing modulesImporting modules

by conven�on, place import statements at the topimport module_name: access func�ons via module_name.func

Example: Example: generator.py as module as module

Variations of an Variations of an import statement statement

from module_name import func: access func�ons directly funcfrom module_name import *: import all names that don't begin with _

not recommended! why?

import module_name as mn: access func�ons via mn.funcfrom module_name import func as f: access func�ons via f

Example: Example: generator.py as module as module

Importing other modulesImporting other modules

there are numerous provided in Python that can be imported

standard modules (h�ps://docs.python.org/3/library/)

https://docs.python.org/3/library/

Scripting in more detailScripting in more detail

can give shebang line to tell terminal what interpreter you are usingallows for execu�on of script without python3

also be sure that the file is executable by running chmod +x file

: system-specific command lineand interpreter parameters

low level details like script flags, filesystem pathssys.argv for simple argument passing

sys (h�ps://docs.python.org/3/library/sys.html)

https://docs.python.org/3/library/sys.html

Example: Example: generator.py as script with argument parsing as script with argument parsing

Scripting in more detailScripting in more detail

another standardlibrary that provides more powerful argument parsing

common theme: different module choices for low-level vs high-levelcontrol

argparse (h�ps://docs.python.org/3/library/argparse.html)

https://docs.python.org/3/library/argparse.html

Example: Example: generator.py with better argument parsing with better argument parsing

TestingTesting

"The first principle is that you must not fool yourself — and you are the easiestperson to fool." — Richard Feynman

we all write tests -- li�le print statements to verify the output, etc.but we (usually) end up throwing them away

Testing using Testing using assert

statements are a simple way to debug beyond print statementsSyntax: assert bool_expression, description

assert (h�ps://docs.python.org/3/reference/simple_stmts.html#the-assert-statement)

https://docs.python.org/3/reference/simple_stmts.html#the-assert-statement

Example: using asserts to test/check Example: using asserts to test/check generator.py

What are unit tests?What are unit tests?

check the func�onality ofspecific pieces of code for correct behavior, in isola�on

contrast with integra�on tests

unit tests (h�ps://en.wikipedia.org/wiki/Unit_tes�ng)

https://en.wikipedia.org/wiki/Unit_testing

Testing using Testing using unittest

is a standard library forunit tes�ng in an object-oriented manneruni�est (h�ps://docs.python.org/3/library/uni�est.html)

subclass the unittest.TestCase class to write custom test casesany method defined in the class star�ng with test_ is considered a test casenumerous self.assert... statements, see

for full detailsmost common is self.assertEqual(a, b): checks that a == b

documenta�on(h�ps://docs.python.org/3/library/uni�est.html#assert-methods)

https://docs.python.org/3/library/unittest.htmlhttps://docs.python.org/3/library/unittest.html#assert-methods

Example: writing unit tests for Example: writing unit tests for generator.py

Test-driven development mindsetTest-driven development mindset

consider: wri�ng tests firstwrite code to pass tests -> makes coding sessions more directedforces you to think about failure points in your code

Test-driven development mindsetTest-driven development mindset

from Obey the Tes�ng Goat (h�ps://www.obeythetes�nggoat.com/)

https://www.obeythetestinggoat.com/

Extended example: Querying WikipediaExtended example: Querying Wikipedia

Goal: build a script that provides Wikipedia summaries of topics to the terminal

HTTP requestsHTTP requests

(hypertext transferprotocol) is how client computers and servers exchange informa�on over theinternet

see the onInternet Basics for more details

HTTP (h�ps://developer.mozilla.org/en-US/docs/Web/HTTP)

shared 19x lecture (h�ps://www.cis.upenn.edu/~cis19x/)

the client (usually your computer's web browser) sends a HTTP request to aspecific URL, and the server responds with data, such as the HTML for awebpage

we can also send and receive requests programma�cally in our Python code

https://developer.mozilla.org/en-US/docs/Web/HTTPhttps://www.cis.upenn.edu/~cis19x/

Example: Wikipedia summariesExample: Wikipedia summaries

wikipedia has an API to extract ar�cle summariesh�ps://en.wikipedia.org/api/rest_v1/page/summary/ar�cle_name(h�ps://en.wikipedia.org/api/rest_v1/page/summary/ar�cle_name)

sending HTTP GET requests will return summary data about the ar�cle

Aside: this is an example of a ("representa�onal

state transfer" paradigm for web services)stateless exchange of informa�on through HTTP requests andresponses

RESTful API(h�ps://en.wikipedia.org/wiki/Representa�onal_state_transfer)

https://en.wikipedia.org/api/rest_v1/page/summary/article_namehttps://en.wikipedia.org/wiki/Representational_state_transfer

Parsing data: JSONParsing data: JSON

data from the internet needs to follow par�cular standards in order to be parsedby machines/code

is a par�cularly popular data standardto do thisJSON (h�ps://www.json.org/json-en.html)

https://www.json.org/json-en.html

Parsing data: JSONParsing data: JSON

JSON concepts map cleanly onto PythonJSON objects {} -> dic�onariesJSON arrays [] -> listsJSON values "", 1, 1.0, true -> strings, ints, floats, bools

use the Python standard libraryfor parsing

json (h�ps://docs.python.org/3/library/json.html)

https://docs.python.org/3/library/json.html

Example: parsing Wikipedia data using Example: parsing Wikipedia data using json and �les and �les

Requests: high-level HTTP APIRequests: high-level HTTP API

is a 3rd party module thatabstracts HTTP response/requests into Python objectsfor reference, compare to lower-level

module in the Python standardlibrary

requests (h�ps://requests.readthedocs.io/en/master/)

urllib(h�ps://docs.python.org/3/library/urllib.html)

https://requests.readthedocs.io/en/master/https://docs.python.org/3/library/urllib.html

Installing 3rd party modulesInstalling 3rd party modules

we use to install third partymodulespip3 install module or python3 -m pip install module

pip (h�ps://docs.python.org/3/installing/index.html)

https://docs.python.org/3/installing/index.html

Example: querying the Wikipedia API using Example: querying the Wikipedia API using requests

Putting everything togetherPutting everything together

TakeawaysTakeaways

module usage and crea�onscript usage and crea�onhow to write tests