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首页Python3入门指南：从2to3升级实战与字符串转型详解

Python3入门指南：从2to3升级实战与字符串转型详解

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"《深入Python3》是一本面向初学者的优秀教程，旨在帮助读者掌握Python3语言。对于那些已经熟悉Python2或拥有原版《Dive Into Python》的程序员，本书提供了从Python2向Python3迁移的指南，特别强调了通过2to3脚本来自动化转换过程。章节1.1 'MINUS LEVEL' 指出，如果读者是Python老手，应直接进入Python3的学习，因为Python3引入了许多语法变化，如print函数升级为内置函数，变量前不再需要加``，等等。案例研究部分详述了将一个非平凡的Python 2库移植到Python 3的经历，这可能对面临类似问题的开发者提供有价值的参考。需要注意的是，迁移过程中可能会遇到挑战，特别是字符串处理的变化。Python 3引入了Unicode字符串处理的优势，使得字符串操作更加灵活和统一。然而，这个过程需要对库的内部工作原理有深入理解，以便找出问题所在并进行修复，尤其是当库中大量依赖于旧的字符串处理方式时。《Dive into Python3》不仅适合新手入门，也适合有一定经验的Python用户了解Python3的新特性，并学会如何在实际项目中迁移和适应新版本的语言。作者通过实例讲解和逐步指导，帮助读者逐步克服语法差异，提升编程技能。"

The next

screen

allows you

to change

your install

location.

You must

install

Python on

your boot

drive, but

due to

limitations of

the installer,

it does not

enforce this.

In truth, I

have never

had the need to change the install location.

From this screen, you can also customize the installation to exclude certain features. If you want to do this,

click the Customize button; otherwise click the Install button.

If you

choose a

Custom

Install, the

installer will

present you

with the

following list

of features:

◦ Python

Framework. This is the guts of Python, and is both selected and disabled because it must be installed.

◦ GUI Applications includes IDLE, the graphical Python Shell which you will use throughout this book. I

strongly recommend keeping this option selected.

◦ UNIX command-line tools includes the command-line python3 application. I strongly recommend keeping

this option, too.

◦ Python Documentation contains much of the information on docs.python.org. Recommended if you are

on dialup or have limited Internet access.

◦ Shell profile updater controls whether to update your shell profile (used in Terminal.app) to ensure that

this version of Python is on the search path of your shell. You probably don’t need to change this.

◦ Fix system Python should not be changed. (It tells your Mac to use Python 3 as the default Python for all

scripts, including built-in system scripts from Apple. This would be very bad, since most of those scripts are

written for Python 2, and they would fail to run properly under Python 3.)

Click the Install button to continue.

Because it

installs

system-wide

frameworks

and binaries

in /usr/

local/bin/,

the installer

will ask you

for an

administrative password. There is no way to install Mac Python without administrator privileges.

Click the OK button to begin the installation.

The installer

will display a

progress

meter while

it installs the

features

you’ve

selected.

Assuming all

went well,

the installer

will give you

a big green

checkmark

to tell you

that the

installation

completed

successfully.

Click the Close button to exit the installer.

Assuming you didn’t change the

install location, you can find the

newly installed files in the

Python 3.1 folder within your

/Applications folder. The

most important piece is IDLE,

the graphical Python Shell.

Double-click IDLE to launch the

Python Shell.

剩余494页未读，继续阅读

CHAPTER-1.WHAT’SNEWIN“DIVEINTO PYTHON3” ❝Isn’tthiswherewecamein?❞ —PinkFloyd,TheWall -1.1.A.K.A.“THEMINUSLEVEL” AreyoualreadyaPythonprogrammer?Didyoureadtheoriginal“DiveIntoPython”?Didyoubuyit onpaper?(Ifso,thanks!)AreyoureadytotaketheplungeintoPython3?…Ifso,readon.(Ifnoneofthat istrue,you’dbebetteroffstartingatthebeginning.) Python3comeswithascriptcalled2to3.Learnit.Loveit.Useit.PortingCodetoPython3with2to3isa referenceofallthethingsthatthe2to3toolcanfixautomatically.Sincealotofthosethingsaresyntax changes,it’sagoodstartingpointtolearnaboutalotofthesyntaxchangesinPython3.(printisnowa function,`x`doesn’twork,&c.) CaseStudy:PortingchardettoPython3documentsmy(ultimatelysuccessful)efforttoportanon-trivial libraryfromPython2toPython3.Itmayhelpyou;itmaynot.There’safairlysteeplearningcurve,since youneedtokindofunderstandthelibraryfirst,soyoucanunderstandwhyitbrokeandhowIfixedit.A lotofthebreakagecentersaroundstrings.Speakingofwhich… Strings.Whew.Wheretostart.Python2had“strings”and“Unicodestrings.”Python3has“bytes”and “strings.”Thatis,allstringsarenowUnicodestrings,andifyouwanttodealwithabagofbytes,youuse thenewbytestype.Python3willneverimplicitlyconvertbetweenstringsandbytes,soifyou’renotsure whichoneyouhaveatanygivenmoment,yourcodewillalmostcertainlybreak.ReadtheStringschapter formoredetails. Bytesvs.stringscomesupagainandagainthroughoutthebook. 1 •InFiles,you’lllearnthedifferencebetweenreadingfilesin“binary”and“text”mode.Reading(andwriting!) filesintextmoderequiresanencodingparameter.Sometextfilemethodscountcharacters,butother methodscountbytes.Ifyourcodeassumesthatonecharacter==onebyte,itwillbreakonmulti-byte characters. •InHTTPWebServices,thehttplib2modulefetchesheadersanddataoverHTTP.HTTPheadersare returnedasstrings,buttheHTTPbodyisreturnedasbytes. •InSerializingPythonObjects,you’lllearnwhythepicklemoduleinPython3definesanewdataformatthat isbackwardlyincompatiblewithPython2.(Hint:it’sbecauseofbytesandstrings.)AlsoJSON,whichdoesn’t supportthebytestypeatall.I’llshowyouhowtohackaroundthat. •InCasestudy:portingchardettoPython3,it’sjustabloodymessofbytesandstringseverywhere. Evenifyoudon’tcareaboutUnicode(ohbutyouwill),you’llwanttoreadaboutstringformattinginPython 3,whichiscompletelydifferentfromPython2. IteratorsareeverywhereinPython3,andIunderstandthemalotbetterthanIdidfiveyearsagowhenI wrote“DiveIntoPython”.Youneedtounderstandthemtoo,becauselotsoffunctionsthatusedtoreturn listsinPython2willnowreturniteratorsinPython3.Ataminimum,youshouldreadthesecondhalfof theIteratorschapterandthesecondhalfoftheAdvancedIteratorschapter. Bypopularrequest,I’veaddedanappendixonSpecialMethodNames,whichiskindoflikethePythondocs “DataModel”chapterbutwithmoresnark. WhenIwaswriting“DiveIntoPython”,alloftheavailableXMLlibrariessucked.ThenFredrikLundhwrote ElementTree,whichdoesn’tsuckatall.ThePythongodswiselyincorporatedElementTreeintothestandard library,andnowitformsthebasisformynewXMLchapter.TheoldwaysofparsingXMLarestillaround, butyoushouldavoidthem,becausetheysuck! AlsonewinPython—notinthelanguagebutinthecommunity—istheemergenceofcoderepositories likeThePythonPackageIndex(PyPI).Pythoncomeswithutilitiestopackageyourcodeinstandardformats anddistributethosepackagesonPyPI.ReadPackagingPythonLibrariesfordetails.

The filename, directory name, or volume label syntax is incorrect. The filename, directory name, or volume label syntax is incorrect. ERROR conda.cli.main_run:execute(47): `conda run python D:\DeepLearning\dive_into_deep_learning\MLP.py` failed. (See above for error)

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3. 检查文件系统：确保你要操作的文件系统没有任何问题。如果你使用的是外部存储设备（例如 USB 驱动器），请确保设备已正确连接并可以正常访问。 4. 检查权限：如果你尝试访问或修改某个目录或文件，确保你具有...

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Python3入门指南：从2to3升级实战与字符串转型详解

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The filename, directory name, or volume label syntax is incorrect. The filename, directory name, or volume label syntax is incorrect. ERROR conda.cli.main_run:execute(47): `conda run python D:\DeepLearning\dive_into_deep_learning\MLP.py` failed. (See above for error)

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