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python100道面试题及解答()全部答案 pycharm 测试过 py3环境)

于 2020-12-11 发布
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python面试题100道答案全部 一般的只写了30个答案题目大概有1、一行代码实现1--100之和2、如何在一个函数内部修改全局变量利用global 修改全局变量3、列出5个python标准库os:提供了不少与操作系统相关联的函数sys: 通常用于命令行参数re: 正则匹配math: 数学运算datetime:处理日期时间

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    完整版,带目录,机器学习必备经典;大部头要用力啃。Machine learning A Probabilistic PerspectiveMachine LearningA Probabilistic PerspectiveKevin P. MurphyThe mit PressCambridge, MassachusettsLondon, Englando 2012 Massachusetts Institute of TechnologyAll rights reserved. No part of this book may be reproduced in any form by any electronic or mechanicalmeans(including photocopying, recording, or information storage and retrieval)without permission inwriting from the publisherFor information about special quantity discounts, please email special_sales@mitpress. mit. eduThis book was set in the HEx programming language by the author. Printed and bound in the UnitedStates of AmLibrary of Congress Cataloging-in-Publication InformationMurphy, Kevin Png:a piobabilistctive/Kevin P. Murphyp. cm. -(Adaptive computation and machine learning series)Includes bibliographical references and indexisBn 978-0-262-01802-9 (hardcover: alk. paper1. Machine learning. 2. Probabilities. I. TitleQ325.5M872012006.31-dc232012004558109876This book is dedicated to alessandro, Michael and stefanoand to the memory of gerard Joseph murphyContentsPreactXXVII1 IntroductionMachine learning: what and why?1..1Types of machine learning1.2 Supervised learning1.2.1Classification 31.2.2 Regression 83 Unsupervised learning 91.3.11.3.2Discovering latent factors 111.3.3 Discovering graph structure 131.3.4 Matrix completion 141.4 Some basic concepts in machine learning 161.4.1Parametric vs non-parametric models 161.4.2 A simple non-parametric classifier: K-nearest neighbors 161.4.3 The curse of dimensionality 181.4.4 Parametric models for classification and regression 191.4.5Linear regression 191.4.6Logistic regression1.4.7 Overfitting 221.4.8Model selection1.4.9No free lunch theorem242 Probability2.1 Introduction 272.2 A brief review of probability theory 282. 2. 1 Discrete random variables 282. 2.2 Fundamental rules 282.2.3B292. 2. 4 Independence and conditional independence 302. 2. 5 Continuous random variable32CONTENTS2.2.6 Quantiles 332.2.7 Mean and variance 332.3 Some common discrete distributions 342.3.1The binomial and bernoulli distributions 342.3.2 The multinomial and multinoulli distributions 352. 3.3 The Poisson distribution 372.3.4 The empirical distribution 372.4 Some common continuous distributions 382.4.1 Gaussian (normal) distribution 382.4.2Dte pdf 392.4.3 The Laplace distribution 412.4.4 The gamma distribution 412.4.5 The beta distribution 422.4.6 Pareto distribution2.5 Joint probability distributions 442.5.1Covariance and correlation442.5.2 The multivariate gaussian2.5.3 Multivariate Student t distribution 462.5.4 Dirichlet distribution 472.6 Transformations of random variables 492. 6. 1 Linear transformations 492.6.2 General transformations 502.6.3 Central limit theorem 512.7 Monte Carlo approximation 522.7.1 Example: change of variables, the MC way 532.7.2 Example: estimating T by Monte Carlo integration2.7.3 Accuracy of Monte Carlo approximation 542.8 Information theory562.8.1Entropy2.8.2 KL dive572.8.3 Mutual information 593 Generative models for discrete data 653.1 Introducti653.2 Bayesian concept learning 653.2.1Likelihood673.2.2 Prior 673.2.3P683.2.4Postedictive distribution3.2.5 A more complex prior 723.3 The beta-binomial model 723.3.1 Likelihood 733.3.2Prior743.3.3 Poster3.3.4Posterior predictive distributionCONTENTS3.4 The Dirichlet-multinomial model 783. 4. 1 Likelihood 793.4.2 Prior 793.4.3 Posterior 793.4.4Posterior predictive813.5 Naive Bayes classifiers 823.5.1 Model fitting 833.5.2 Using the model for prediction 853.5.3 The log-sum-exp trick 803.5.4 Feature selection using mutual information 863.5.5 Classifying documents using bag of words 84 Gaussian models4.1 Introduction974.1.1Notation974. 1.2 Basics 974. 1.3 MlE for an mvn 994.1.4 Maximum entropy derivation of the gaussian 1014.2 Gaussian discriminant analysis 1014.2.1 Quadratic discriminant analysis(QDA) 1024.2.2 Linear discriminant analysis (LDA) 1034.2.3 Two-claSs LDA 1044.2.4 MLE for discriminant analysis 1064.2.5 Strategies for preventing overfitting 1064.2.6 Regularized LDA* 104.2.7 Diagonal LDA4.2.8 Nearest shrunken centroids classifier1094.3 Inference in jointly Gaussian distributions 1104.3.1Statement of the result 1114.3.2 Examples4.3.3 Information form 1154.3.4 Proof of the result 1164.4 Linear Gaussian systems 1194.4.1Statement of the result 1194.4.2 Examples 1204.4.3 Proof of the result1244.5 Digression: The Wishart distribution4.5. 1 Inverse Wishart distribution 1264.5.2 Visualizing the wishart distribution* 1274.6 Inferring the parameters of an MVn 1274.6.1 Posterior distribution of u 1284.6.2 Posterior distribution of e1284.6.3 Posterior distribution of u and 2* 1324.6.4 Sensor fusion with unknown precisions 138
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  • ISO16750-3-2012
    ISO16750-3-2012Road vehicles — Environmentalconditions and testing for electricaland electronic equipment —Part 3:Mechanical loadsContents PageForeword.............................................................................................................................................Iso16750-3:2012[EContentsPageForewordScope12Normative references1Terms and definitions4Tests and requirements4.1ibration4.2 Mechanical shock274.3 Free fall…294.4 Surface strength/ scratch and abrasion resistance294.5 Gravel bombardmentCode letters for mechanical loads29Documentation…,…………111111130Annex A (informative) Guideline for the development of test profiles for vibration tests.32Annex B (informative) Recommended mechanical requirements for equipment depending on themounting location44Bibliography46C ISO 2012-All rights reservedIso16750-3:2012EForewordISo (the International Organization for Standardization) is a worldwide federation of national standardsbodies (Iso member bodies). The work of preparing International Standards is normally carried outthrough iso technical committees. Each member body interested in a subject for which a technicalcommittee has been established has the right to be represented on that committee. Internationaorganizations, governmental and non-governmental, in liaison with ISO, also take part in the workIso collaborates closely with the International Electrotechnical Commission (IEC) on all matters ofelectrotechnical standardizationInternational Standards are drafted in accordance with the rules given in the ISo/IEC Directives, Part 2The main task of technical committees is to prepare lnternational standards. draft InternationalStandards adopted by the technical committees are circulated to the member bodies for votingublication as an International Standard requires approval by at least 75 of the member bodiescasting a voteAttention is drawn to the possibility that some of the elements of this document may be the subject ofpatent rights. ISO shall not be held responsible for identifying any or all such patent rightsIso 16750-3 was prepared by Technical Committee ISO/TC 22, Road vehicle, Subcommittee SC 3,Electrical and electronical equipment.This third edition cancels and replaces the second edition (Iso 16750-3: 2007), which has beentechnically revisedISo 16750 consists of the following parts, under the general title road vehicles-Environmental conditionsand testing for electrical and electronic equipment:Part 1: GeneralPart 2: electrical loadsPart 3: Mechanical loadsPart 4: Climatic loadsPart 5: chemical loadso ISO 2012-All rights reservedINTERNATIONAL STANDARDIso16750-3:2012(E)Road vehicles- Environmental conditions and testing forelectrical and electronic equipmentPart 3Mechanical loads1 ScopeThis part of IS0 16750 applies to electric and electronic systems/components for road vehicles. Itdescribes the potential environmental stresses and specifies tests and requirements recommended forthe specific mounting location on/in the vehicleThis part of iso 16750 describes mechanical loads2 Normative referencesThe following referenced documents are indispensable for the application of this document. For datedreferences, only the edition cited applies For undated references, the latest edition of the referenceddocument (including any amendments applies.Iso16750-1, Road vehicles- Environmental conditions and testing forelectrical andelectronicequipment-Part 1: GeneralIEC 60068-2, 6, Environmental testing- Part 2-6: Testing, Test Fc: Vibration SinusoidalIEC60068-2, 14, Basicenvironmental testing procedures- Part 2-14: Tests-Test Nb: Change oftemperatureTEC 60068-2, 64, Environmental testing Part 2-64: Test methods -Test Fh -Vibration, broad-bandrandom(digital control)and guidanceIEC 60068-2, 80, Environmental testing- Part 2-80: Tests- Test Fi: Vibration - Mixed mode testingIEC 60068-2-31, Environmental testing procedures- Part 2: Tests; Test Ec: Free fall, Clause 5.23 Terms and definitionsFor the purposes of this document, the terms and definitions given in Iso 16750-1 app4 Tests and requirements4.1 Vibration41.1 GeneralThe vibration test metho ds specified consider various levels of vibration severities applicable to on-board electrical and electronic equipment. It is recommended that the vehicle manufacturer andsupplier choose the test method, the environmental temperature and vibration parameters dependingon the specific mounting locationFollowing the expressions in MIL-STD please noticeC ISO 2012-All rights reservedIso16750-3:2012EWhen applied properly, the environmental management and engineering processes described in this partof Iso 16750 can be of enormous value in generating confidence in the environmental worthiness andoverall durability. However, it is important to recognize that there are limitations inherent in laboratorytesting that make itimperative to use proper caution and engineering judgement when extrapolating theselaboratory results to results that may be obtained under actual service conditions. In many cases, realworld environmental stresses (singularly orin combination cannot be duplicated practically or reliably intestlaboratories. Therefore, users of this part of Iso 16750 should not assume that a system or componentthat passes laboratory tests of this part of Iso 16750 would also pass field/ fleet verification trialsThe specified values are the best estimation one can get up to the moment when results frommeasurements in the car are received - but they do not replace a car measurement!The specified values apply to direct mounting in defined mounting locations. Using a bracket formounting can resultin higher or lower loads. If the device under test ( DUT)is used in the vehicle with abracket then all vibration and mechanical shock test shall be done with this bracketCarry out the vibration with the dut suitably mounted on a vibration table. The mounting method (sused shall be noted in the test report. Carry out the frequency variation by logarithmic sweeping of 0,5octave/minute for sinusoidal tests and the sinusoidal part of sine on random tests. The scope of therecommended vibration tests is to avoid malfunctions and breakage mainly due to fatigue in the fieldTesting for wear has special requirements and is not covered in this part of ISo 16750Loads outside of the designated test frequency ranges are to be considered separatelNOTE Deviations from the load on the DUT can result, should vibration testing be carried out according tothis part of Iso 16750 on a heavy and bulky dut, as mounting rigidity and dynamic reaction on the vibrator tableexcitation are different compared to the situation in the vehicle. This deviation can be minimized by applying theaverage control method(see Annex A)Application of the weighted average control method according to IEC 60068-2, 64 is to be agreed uponSubject the dut during the vibration test to the temperature cycle according to iEC 60068-2, 14, withelectric operation according to diagram 1. Alternatively, a test at constant temperature may be agreed onOperate the dutelectrically as indicatedin Figure l at Tmin(Short functional testafterthe dUT completelyreached Tmin). This functional test shall be as short as possible- only long enough to check the properperformance of the dUt. This minimizes self-heating of the dUT. Additional electrical operation of theDUT between 210 min and 410 min of the cycle (see Figure 1)Additional drying of test chamber air is not permittedIn the vehicle, vibration stress can occur together with extremely low or high temperatures; for thisreason, this interaction between mechanical and temperature stress is simulated in the test, too. afailure mechanism is, for example, a plastic part of a system/component, which mellows due to the hightemperature and cannot withstand the acceleration under this condition2o ISO 2012-All rights reservedIso16750-3:2012[EYmax20aburditt0100200300400500600yY temperature[°C]x time [ minIa Operating mode 3.2 according to ISo 16750-1.b Operating mode 2. 1 according to ISo 16750-1One cycleFigure 1-Temperature profile for the vibration testTable 1- Temperature versus time for the vibration testTimeTemperaturemin°C0206040150-4021020300max41048020See Is016750-44.1.2 Tests4.1.2.1 Test I- Passenger car, engine4.1.2.1.1 PurposeThis test checks the dUt for malfunctions and breakage caused by vibrationThe vibrations of a piston engine can be split up into two kinds: Sinusoidal vibration which results from theunbalanced mass forces in the cylinders and random noise due to all other vibration-schemes of an engine,C ISO 2012-All rights reserved3Iso16750-3:2012Ee.g. closing of valves. In the lowest frequency range from 10 Hz to 100 Hz the influence of rough-roadconditions is taken into account. The main failure to be identified by this test is breakage due to fatigueNOTE 1 Road profile usually has negligible impact on engine-mounted components. Shock inputs are effectivelysolated by suspension, and engine-mounting systemsThe test profiles specified in the following clauses apply to loads generated by(four strokereciprocating enginesNotE 2 If the dut is to be tested for a specific resonance effect, then a resonance dwell test according to 8.3.2of IEC 60068-2, 6: 2007 can also be applied4.12.1.2Test4.1.2.1.2.1 GeneralIt is required to perform this test as a mixed mode vibration test according to IEC 60068-2, 80NOTE The test duration is based on A 4. The temperature in the chamher is above room temperature (rt)atthe end of the test (2 3/4 temperature cycles4.1.2.1.2.2 Sinusoidal vibrationPerform the test according to IEC 60068-2, 6, but using a sweep rate of s 0,5 octave/minute. Use a testduration of 22 h for each plane of the dUTUse curve l in Table 2/ Figure 2 for DUT intended for mounting on engines with 5 cylinders or fewerUse curve 2 in Table 2/Figure 2 for dUT test intended for mounting on engines with 6 cylinders or moreBoth curves may be combined to cover all engine types in one test2502001501005050100150200250300350400450500ⅩKeyamplitude of acceleration [m/s2IXfrequency [Hzcurve1(≤5 cylinders)curve 2(5 cylindersFigure 2- Vibration severity curves4o ISO 2012-All rights reservedIso16750-3:2012[ETable 2- values for max acceleration versus frequencyCurve 1(see Figure 2FrequencyAmplitude of accelerationHz100100200200240200270100440100Curve 2(see Figure 2)FrequencyAmplitude of accelerationHm/s2100100150150440150CombinationFrequencyAmplitude of accelerationH1001001501502002002402002551504401504,1.21.2.3 Random vibrationPerform the test according to IEC 60068-2, 64. Use a test duration of 22 h for each plane of the DUTThe r.m.s. acceleration value shall be 181 m/s2The psd versus frequency are referred to in Figure 3 and Table 3NoTE The Power Spectral Density(PSD)values (random vibration] are reduced in the frequency range of thesinusoidal vibration testC ISO 2012-All rights reserved5Iso16750-3:2012EY100100,110100100010000KeyY PSD [(m/s2)2/HzX frequency [Hz]Figure 3- PSD of acceleration versus frequencyTable 3- Values for frequency and PsDFrequencyPSDH:(m/s2)2/Hz1010100103000,5150020200024.1.2.1.3 RequirementBreakage shall not occur.Functional status a see iso 16750-1) is required during operating mode 3.2 as defined in ISo 16750-1and functional status C during periods with other operating modes4.1.2.2 Test II-Passenger car, gearbox4.1.2.2.1 PurposeThis test checks the dut for malfunctions and breakage caused by vibrationThe vibrations of a gearbox can be split up into two kinds which result partly from sinusoidal vibrationfrom unbalanced mass forces of the engine(e. g dominating orders) in the frequency range from 100 Hzto 440 Hz and vibration from the friction of the gear wheels and other schemes, which are tested in therandom part. In the lowest frequency range from 10 Hz to 100 Hz the influence of rough-road conditionsis taken into account The main failure to be identified by this test is breakage due to fatigueChanging the gears can create additional mechanical shock and shall be considered separatey brationsThe test profiles specified in the following subclauses apply to loads generated by gearbox vibo ISO 2012-All rights reserved
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