Two Scoops of Django Best Practices for Django 1.8

521 Pages·2015·11.837 MB·English

by  Daniel Roy Greenfeld, Audrey Roy Greenfeld

Two Scoops of Django
Best Practices For Django 1.8
Daniel Roy Greenfeld
Audrey Roy Greenfeld
TwoScoopsofDjango:BestPracticesforDjango1.8
(cid:315)irdEdition,2015-05-20
byDanielRoyGreenfeldandAudreyRoyGreenfeld
Copyright⃝c 2013-2015DanielRoyGreenfeld,AudreyRoyGreenfeld,andTwoScoopsPress.
Allrightsreserved.(cid:315)isbookmaynotbereproducedinanyform,inwholeorinpart,withoutwrittenpermissionfromthe
authors,exceptinthecaseofbriefquotationsembodiedinarticlesorreviews.
LimitofLiabilityandDisclaimerofWarranty:(cid:315)eauthorshaveusedtheirbesteffortsinpreparingthisbook,andthe
informationprovidedherein“asis.”(cid:315)einformationprovidedissoldwithoutwarranty,eitherexpressorimplied.Neitherthe
authorsnorCartwheelWebwillbeheldliableforanydamagestobecausedeitherdirectlyorindirectlybythecontentsof
thisbook.
Trademarks:Ratherthanindicatingeveryoccurrenceofatrademarkednameassuch,thisbookusesthenamesonlyinan
editorialfashionandtothebene(cid:320)tofthetrademarkownerwithnointentionofinfringementofthetrademark.
FirstPrinting,April2015
Formoreinformation,visithttps://twoscoopspress.com.
iii
iv
Dedication
For Malcolm Tredinnick
1971-2013
We miss you.
http://2scoops.co/malcolm-tredinnick-memorial
v
About the Dedication
MalcolmTredinnickwasn’tjustaDjangocoredeveloperandreviewerof“TwoScoopsofDjango:
BestPracticesforDjango1.5.”Tous,hewasmuch,muchmore.
DanielhadworkedwithMalcolmTredinnickinthesummerof2010,butwe(cid:320)rstmethiminperson
atDjangoCon2010.Hewasfunnyandcharming,sharplyopinionatedbutalwaysagentleman;we
instantlybecameclosefriends.
In2012,whenweco-organizedthe(cid:320)rstPyConPhilippines,assoonaswetoldhimaboutit,Mal-
colminstantlydeclaredhewascoming.Hegavetwomemorabletalksandrananimpromptuall-day
Djangotutorial.HealsopushedandencouragedthelocalcommunitytoworkonFilipinolanguage
translationsforDjango,includingTagalog,Tausug,Cebuano,andmore.
Aftertheconference,westartedworkingonabookaboutDjangobestpractices.Wegatheredfriends
andcolleaguestohelpusastechnicalreviewers.MalcolmTredinnickbecamethemostactiveofthem.
Hewasourmentorandforcedustodigdeeperandworkharder.Hedidthiswhileworkingaday
jobastheleaderofacombinedRailsandHaskellteam;Malcolmwasatrueprogramminglanguage
polyglot.
Forourbook,heprovidedsomuchassistanceandguidancewetriedto(cid:320)gureoutawaytoinclude
him in the author credits. When we told him about our dilemma, he laughed it off saying, “For a
book called ‘Two Scoops’, you can’t have three authors.” We suggested he share credit with us on
a second book, and he refused, saying he preferred to just comment on our work. He said that he
wantedpeopletohaveproperreferences,andforhim,simplyreviewingourworkwascontributing
tothegreatergood.Eventuallythetwoofusquietlyplannedtosomehowcoercehimintobeinga
co-authoronafuturework.
Aftermonthsofeffort,wereleasedthe(cid:320)rstiterationonJanuary17th,2013.Malcolmsteppedback
fromTwoScoopsofDjango,butwestayedintouch.SinceMalcolmwasunabletoattendPyCon
US2013weweren’tsurewhenwewouldmeethimagain.
Twomonthslater,onMarch17th,2013,Malcolmpassedaway.
We knew Malcolm for less than three years and yet he made an incredible difference in our lives.
We’veheardmanysimilarstoriesinthecommunityaboutMalcolm;Hewasafriendandmentorto
countlessothersaroundtheworld.Hislastlessontouswentbeyondcodeorwriting,hetaughtus
tonevertakeforgrantedfriends,family,mentors,andteachers.
Contents
Dedication v
AbouttheDedication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vi
Authors’Notes xxvii
AFewWordsFromDanielRoyGreenfeld . . . . . . . . . . . . . . . . . . . . . . . . . xxvii
AFewWordsFromAudreyRoyGreenfeld . . . . . . . . . . . . . . . . . . . . . . . . xxviii
Introduction xxix
AWordAboutOurRecommendations . . . . . . . . . . . . . . . . . . . . . . . . . . xxix
WhyTwoScoopsofDjango? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxx
BeforeYouBegin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxxi
(cid:315)isbookisintendedforDjango1.8andPython2.7.x/3.3.3+ . . . . . . . . . . . . xxxi
EachChapterStandsOnItsOwn . . . . . . . . . . . . . . . . . . . . . . . . . . xxxi
ConventionsUsedin(cid:315)isBook. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxxii
CoreConcepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxxiii
KeepItSimple,Stupid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxxiii
FatModels,UtilityModules,(cid:315)inViews,StupidTemplates . . . . . . . . . . . . xxxiv
StartWithDjangoByDefault . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxxiv
BeFamiliarwithDjango’sDesignPhilosophies . . . . . . . . . . . . . . . . . . . xxxiv
(cid:315)eTwelve-FactorApp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxxv
OurWritingConcepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxxv
ProvidetheBestMaterial . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxxv
StandontheShouldersofGiants . . . . . . . . . . . . . . . . . . . . . . . . . . . xxxv
ListentoOurReadersandReviewers . . . . . . . . . . . . . . . . . . . . . . . . xxxvi
PublishErrata . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxxvi
1 CodingStyle 1
1.1 (cid:315)eImportanceofMakingYourCodeReadable . . . . . . . . . . . . . . . . . . 1
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Contents
1.2 PEP8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.2.1 (cid:315)e79-CharacterLimit . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.3 (cid:315)eWordonImports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.4 UseExplicitRelativeImports . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.5 AvoidUsingImport* . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.6 DjangoCodingStyle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.6.1 ConsidertheDjangoCodingStyleGuidelines . . . . . . . . . . . . . . . 9
1.6.2 UseUnderscoresinURLPatternNamesRather(cid:315)anDashes. . . . . . . 9
1.6.3 UseUnderscoresinTemplateBlockNamesRather(cid:315)anDashes . . . . . 10
1.7 ChooseJS,HTML,andCSSStyleGuides . . . . . . . . . . . . . . . . . . . . . 10
1.7.1 JavaScriptStyleGuides . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
1.7.2 HTMLandCSSStyleGuides . . . . . . . . . . . . . . . . . . . . . . . 11
1.8 NeverCodetotheIDE(OrTextEditor) . . . . . . . . . . . . . . . . . . . . . . 11
1.9 Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2 (cid:315)eOptimalDjangoEnvironmentSetup 13
2.1 UsetheSameDatabaseEngineEverywhere . . . . . . . . . . . . . . . . . . . . 13
2.1.1 YouCan’tExamineanExactCopyofProductionDataLocally . . . . . . 13
2.1.2 DifferentDatabasesHaveDifferentFieldTypes/Constraints . . . . . . . 14
2.1.3 FixturesAreNotaMagicSolution . . . . . . . . . . . . . . . . . . . . . 15
2.2 UsePipandVirtualenv . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.3 InstallDjangoandOtherDependenciesviaPip . . . . . . . . . . . . . . . . . . 17
2.4 UseaVersionControlSystem . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
2.5 Optional:IdenticalEnvironments . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.5.1 VagrantandVirtualBox . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.6 Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
3 HowtoLayOutDjangoProjects 21
3.1 Django1.8’sDefaultProjectLayout. . . . . . . . . . . . . . . . . . . . . . . . . 21
3.2 OurPreferredProjectLayout . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
3.2.1 TopLevel:RepositoryRoot. . . . . . . . . . . . . . . . . . . . . . . . . 23
3.2.2 SecondLevel:ProjectRoot . . . . . . . . . . . . . . . . . . . . . . . . . 23
3.2.3 (cid:315)irdLevel:Con(cid:320)gurationRoot . . . . . . . . . . . . . . . . . . . . . . 23
3.3 SampleProjectLayout. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
3.4 WhatAbouttheVirtualenv? . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
3.5 GoingBeyondstartproject . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
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