absolute导入
you’vegottenuptospeedonhowtowriteimportstatementsandhowtostylethemlikeapro.nowit’stimetolearnalitttlemoreaboutaboutabsoluteimpprotete
anabsoluteimportspecifiestheresourcetobeimportedusingitsfullpathfromtheproject’sroot folder。
syntax和practical examples
let’ssayyouhavethefollowingdirectorystructure :
() module1.py
() module2.py
there’sa directory，project，whichcontainstwosub-directories，package1and package2. the package1directoryhastwofiles，mory
the package2directoryhasthreefiles 3360 two modules，module3.pyandmodule4.py，and an initialization file，_ _ init _.py su su py
let’sassumethefollowing :
package1/module2. pycontainsafunction，function1。
package2/_ _ init _.pycontainsaclass，class1。
包2/sub包1/module5. pycontainsafunction，function2。
thefollowingarepracticalexamplesofabsoluteimports :
从包1导入模块1
from package1. module 2导入功能1
从包2导入类1
从包2.sub包1.module 5导入功能2
notethatyoumustgiveadetailedpathforeachpackageorfile，from the top-levelpackagefolder.thisissomewhatsimilartoitsfilepath，)
Pros and Cons of Absolute Imports
absoluteimportsarepreferredbecausetheyarequiteclearandstraightforward.itiseasytotellexactlywheretheimportedresourceis， justbylookingatthestatement.additionally，absoluteimportsremainvalidevenifthecurrentlocationoftheimportstatemementchantes.iontchanges.ion
Sometimes，however，absoluteimportscangetquiteverbose，dependingonthecomplexityofthedirectorystructure.imaginehavingastatatatate
来自包1.sub包2.sub包3.sub包4.module 5导入功能6
that’sridiculous，right？ Luckily，relativeimportsareagoodalternativeinsuchcases！
可撤销导入
arelativeimportspecifiestheresourcetobeimportedrelativetothecurrentlocation-thatis， thelocationwheretheimportstatementis.therearetwotypesofrelativeimports 3360 implicitandexplicit.implicitrelativeimportshave port
syntax和practical examples
thesyntaxofarelativeimportdependsonthecurrentlocationaswellasthelocationofthemodule，package，orobjecttobeimported.hereare
from.some _ moduleimportsome _ class
from . some _ packageimportsome _ function
from . import some_class
youcanseethatthereisatleastonedotineachimportstatementabove.relativeimportsmakeuseofdotnotationtospecifylocation。
asingledotmeansthatthemoduleorpackagereferencedisinthesamedirectoryasthecurrentlocation.twodotsmeanthatitisintheparentdirec tdirec atis，thedirectoryabove.threedotsmeanthatitisinthegrandparentdirectory，and soon.thiswillprobablybefamiliartoyouifyouseauseared
let’sassumeyouhavethesamedirectorystructureasbefore :
() module1.py
() module2.py
召回文件内容：
package1/module2. pycontainsafunction，function1。
package2/_ _ init _.pycontainsaclass，class1。
包2/sub包1/module5. pycontainsafunction，function2。
youcanimportfunction1into the package1/module1. pyfilethisway :
# package1/module1.py
from .module2 import function1
you’duseonlyonedotherebecausemodule2. pyisinthesamedirectoryasthecurrentmodule，which ismodule1.py。
youcanimportclass1and function2into the package2/module3. pyfilethisway :
# package2/module3.py
from . import class1
from.sub package1. module 5导入功能2
in the first导入语句，thesingledotmeansthatyouareimportingclass1fromthecurrentpackage.rememberthatimportingapackagessssess
In the second import statement，you’duseasingledotagainbecausesubpackage1isinthesamedirectoryasthecurrentmodule，whichismodule
资料来源： https://www.cn blogs.com/Chester-cs/p/13193634.html