FAFU机器学习 02asicsfython)中文.pptx

Python（）的基础;面向对象程序设计;自我;上课;方法;init方法;机器学习基础;2020/12/3;类和对象变量（）;2020/12/3;2020/12/3;Inheritance (继承);School Member;Teacher;Student;Python之特殊方法;;;;;;;;;;;;Why Use Classes;Example;Class Shape;Class Circle;;;;Input and Output;Input from user The input() function takes a string as argument and displays it to the user. Then it waits for the user to type something and press the return key. Once the user has entered and pressed the return key, the input() function will then return that text the user has entered. ;;;;;;Exceptions (异常);;;Handling Exceptions (异常处理) We can handle exceptions using the try…except statement. We basically put our usual statements within the try-block and put all our error handlers in the except-block.;Raising Exceptions （抛出异常） You can raise exceptions using the raise statement by providing the name of the error/exception and the exception object that is to be thrown. The error or exception that you can raise should be a class which directly or indirectly must be a derived class of the Exception class.;2020/12/3;Try … Finally （try … finally语句） Suppose you are reading a file in your program. How do you ensure that the file object is closed properly whether or not an exception was raised? This can be done using the finally block.;2020/12/3;2020/12/3;The with statement (with语句) Acquiring a resource in the try block and subsequently releasing the resource in the finally block is a common pattern. Hence, there is also a with statement that enables this to be done in a clean manner:;numpy, scipy, matplotlib, Scikit-learn;;Numpy数组（1、数组初探）;NumPy的数组中比较重要ndarray对象属性有： ndarray.ndim：数组的维数（即数组轴的个数），等于秩。最常见的为二维数组（矩阵）。 ndarray.shape：数组的维度。为一个表示数组在每个维度上大小的整数元组。例如二维数组中，表示数组的“行数”和“列数”。ndarray.shape返回一个元组，这个元组的长度就是维度的数目，即ndim属性。 ndarray.size：数组元素的总个数，等于shape属性中元组元素的乘积。 ndarray.dtype：表示数组中元素类型的对象，可使用标准的Python类型创建或指定dtype。另外也可使用前一篇文章中介绍的NumPy提供的数据类型。 ndarray.itemsize：数组中每个元素的字节大小。例如，一个元素类???为float64的数组itemsiz属性值为8(float64占用64个bits，每个字节长度为8，所以64/8，占用8个字节。ndarray.data：包含实