


Why Does Multiprocessing Example Result in \'AttributeError\' with Built-in Functions?
Why Multiprocessing Example Gives AttributeError
In an attempt to delve into multiprocessing, an individual encountered an AttributeError while adapting the introductory example from the documentation:
<code class="python">from multiprocessing import Pool def f(x): return x*x if __name__ == '__main__': with Pool(5) as p: print(p.map(f, [1, 2, 3]))</code>
The error: "AttributeError: can't get attribute 'f' on
To resolve this issue, it's important to understand that multiprocessing.Pool has a peculiar design feature. As noted in Python issue #25053, Pool sometimes falters when working with objects not defined in imported modules. As a workaround, you can define your function in a separate file and import the module.
Here's an example:
defs.py:
<code class="python">def f(x): return x*x</code>
run.py:
<code class="python">from multiprocessing import Pool import defs if __name__ == '__main__': with Pool(5) as p: print(p.map(defs.f, [1, 2, 3]))</code>
This modification should resolve the AttributeError. However, it's worth noting that the given example in the documentation might not be the most suitable for beginners due to this potential issue.
The above is the detailed content of Why Does Multiprocessing Example Result in \'AttributeError\' with Built-in Functions?. For more information, please follow other related articles on the PHP Chinese website!

Pythonusesahybridapproach,combiningcompilationtobytecodeandinterpretation.1)Codeiscompiledtoplatform-independentbytecode.2)BytecodeisinterpretedbythePythonVirtualMachine,enhancingefficiencyandportability.

ThekeydifferencesbetweenPython's"for"and"while"loopsare:1)"For"loopsareidealforiteratingoversequencesorknowniterations,while2)"while"loopsarebetterforcontinuinguntilaconditionismetwithoutpredefinediterations.Un

In Python, you can connect lists and manage duplicate elements through a variety of methods: 1) Use operators or extend() to retain all duplicate elements; 2) Convert to sets and then return to lists to remove all duplicate elements, but the original order will be lost; 3) Use loops or list comprehensions to combine sets to remove duplicate elements and maintain the original order.

ThefastestmethodforlistconcatenationinPythondependsonlistsize:1)Forsmalllists,the operatorisefficient.2)Forlargerlists,list.extend()orlistcomprehensionisfaster,withextend()beingmorememory-efficientbymodifyinglistsin-place.

ToinsertelementsintoaPythonlist,useappend()toaddtotheend,insert()foraspecificposition,andextend()formultipleelements.1)Useappend()foraddingsingleitemstotheend.2)Useinsert()toaddataspecificindex,thoughit'sslowerforlargelists.3)Useextend()toaddmultiple

Pythonlistsareimplementedasdynamicarrays,notlinkedlists.1)Theyarestoredincontiguousmemoryblocks,whichmayrequirereallocationwhenappendingitems,impactingperformance.2)Linkedlistswouldofferefficientinsertions/deletionsbutslowerindexedaccess,leadingPytho

Pythonoffersfourmainmethodstoremoveelementsfromalist:1)remove(value)removesthefirstoccurrenceofavalue,2)pop(index)removesandreturnsanelementataspecifiedindex,3)delstatementremoveselementsbyindexorslice,and4)clear()removesallitemsfromthelist.Eachmetho

Toresolvea"Permissiondenied"errorwhenrunningascript,followthesesteps:1)Checkandadjustthescript'spermissionsusingchmod xmyscript.shtomakeitexecutable.2)Ensurethescriptislocatedinadirectorywhereyouhavewritepermissions,suchasyourhomedirectory.


Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

Hot Tools

mPDF
mPDF is a PHP library that can generate PDF files from UTF-8 encoded HTML. The original author, Ian Back, wrote mPDF to output PDF files "on the fly" from his website and handle different languages. It is slower than original scripts like HTML2FPDF and produces larger files when using Unicode fonts, but supports CSS styles etc. and has a lot of enhancements. Supports almost all languages, including RTL (Arabic and Hebrew) and CJK (Chinese, Japanese and Korean). Supports nested block-level elements (such as P, DIV),

EditPlus Chinese cracked version
Small size, syntax highlighting, does not support code prompt function

SecLists
SecLists is the ultimate security tester's companion. It is a collection of various types of lists that are frequently used during security assessments, all in one place. SecLists helps make security testing more efficient and productive by conveniently providing all the lists a security tester might need. List types include usernames, passwords, URLs, fuzzing payloads, sensitive data patterns, web shells, and more. The tester can simply pull this repository onto a new test machine and he will have access to every type of list he needs.

SublimeText3 English version
Recommended: Win version, supports code prompts!

PhpStorm Mac version
The latest (2018.2.1) professional PHP integrated development tool
