slice | 易学教程

Converting nested lists of data into multidimensional Numpy arrays

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问题 In the code below I am building data up in a nested list. After the for loop what I would like is to cast it into a multidimensional Numpy array as neatly as possible. However, when I do the array conversion on it, it only seems to convert the outer list into an array. Even worse when I continue downward I wind up with dataPoints as shape (100L,) ...so an array of lists where each list is my data (obviously I wanted a (100,3) ). I have tried fooling with numpy.asanyarray() also but I can't

Make an object that behaves like a slice

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问题 How can we make a class represent itself as a slice when appropriate? This didn't work: class MyThing(object): def __init__(self, start, stop, otherstuff): self.start = start self.stop = stop self.otherstuff = otherstuff def __index__(self): return slice(self.start, self.stop) Expected output: >>> thing = MyThing(1, 3, 'potato') >>> 'hello world'[thing] 'el' Actual output: TypeError: __index__ returned non-(int,long) (type slice) Inheriting from slice doesn't work either. 回答1: TLDR: It's

golang 命令行参数解析 hflag

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简介 hflag 是被设计用来替代标准的 flag 库，提供更强大更灵活的命令行解析功能，相比标准库， hflag 有如下特点支持可选参数和必选参数支持参数缩写支持位置参数，位置参数可以出现在任意位置支持 bool 参数简写 ( -aux 和 -a -u -x 等效) 支持值参数缩写 ( -p123456 和 -p 123456 等效) 更多类型的支持，支持 net.IP ， time.Time ， time.Duration ， []int , []string 的解析更友好的用法帮助提供一套更简洁的 api 完全兼容 flag 接口用法 hflag 提供两套 api ，一套完全兼容标准库的 flag 接口，另一套类似 python 的 argparse 先定义 flag ，在使用时从 flag 中获取新接口 package main import ( "fmt" "github.com/hpifu/go-kit/hflag" ) func main() { hflag.AddFlag("int", "int flag", hflag.Required(), hflag.Shorthand("i"), hflag.Type("int"), hflag.DefaultValue("123")) hflag.AddFlag("str", "str flag",

Dynamic Python Array Slicing

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I am facing a situation where I have a VERY large numpy.ndarray (really, it's an hdf5 dataset) that I need to find a subset of quickly because they entire array cannot be held in memory. However, I also do not want to iterate through such an array (even declaring the built-in numpy iterator throws a MemoryError ) because my script would take literally days to run. As such, I'm faced with the situation of iterating through some dimensions of the array so that I can perform array-operations on pared down subsets of the full array. To do that, I need to be able to dynamically slice out a subset

Error rendering data with Javascript / KendoUI autocomplete - Object #<Object> has no method 'slice' - how to resolve?

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问题 I am following the Using Kendo UI with MVC4 WebAPI OData and EF article. After installing KendoUI and making sure all references are set, I type in three characters, and get the following error: Uncaught TypeError: Object # has no method 'slice' Root of the Problem To save reading through the updates: Through debugging I found that the issue is that JS is expecting to parse an array, where it isn't available in the data - at the root. In the data hierarchy, it's one level in. Original Problem

How to enumerate a slice using the original indices?

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问题 If I want to enumerate an array (say for a map() function where I would need to use the index of an element together with its value), I could use enumerate() function. E.g.: import Foundation let array: [Double] = [1, 2, 3, 4] let powersArray = array.enumerate().map() { pow($0.element, Double($0.index)) } print("array == \(array)") print("powersArray == \(powersArray)") // array == [1.0, 2.0, 3.0, 4.0] // powersArray == [1.0, 2.0, 9.0, 64.0] <- As expected Now, if I want to use some sub

Append not thread-safe?

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问题 I noticed that if I tried appending to a slice using goroutines inside a for loop, there would be instances where I would get missing/blank data: destSlice := make([]myClass, 0) var wg sync.WaitGroup for _, myObject := range sourceSlice { wg.Add(1) go func(closureMyObject myClass) { defer wg.Done() var tmpObj myClass tmpObj.AttributeName = closureMyObject.AttributeName destSlice = append(destSlice, tmpObj) }(myObject) } wg.Wait() Sometimes, when I print all AttributeName s from destSlice ,

How to slice a batch and apply an operation on each slice in TensorFlow

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I am a beginner with TensorFlow, I am trying to implement a function that takes a batch as input. It has to slice this batch into several ones, apply some operations on them, then concatenate them to build a new tensor to return. Through my readings, I found there are some implemented function like input_slice_producer and batch_join but I didn't get to work with them. I attached what I've found as solution below, but it's kinda slow, not proper and incapable of detecting the current size of batch. Does any know a better way of doing this? def model(x): W_1 = tf.Variable(tf.random_normal([6,1]

Delete all elements in an array corresponding to Boolean mask

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I have a Boolean mask that exists as 2-D numpy array (Boolean Array) array([[ True, True, True, True, True, True, True], [ True, True, True, True, True, True, True], [ True, True, True, True, True, True, True], [ True, True, True, True, True, True, True], [False, False, False, False, False, False, False], [False, False, False, False, False, False, False], [False, False, False, False, False, False, False]], dtype=bool) I also have a separate 2-D numpy array of values that is of the same dimensions as the Boolean mask (Values Array) array([[ 19.189 , 23.2535, 23.1555, 23.4655, 22.6795, 20.3295,

How can I slice a string like Python does in Perl 6?

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In Python, I can splice string like this: solo = A quick brown fox jump over the lazy dog solo[3:5] I know substr and comb is enough, I want to know if it's possible, However. Should I use a role to do this? How to slice a string Strings (represented as class Str ) are seen as single values and not positional data structures in Perl 6, and thus can't be indexed/sliced with the built-in [ ] array indexing operator. As you already suggested, comb or substr is the way to go: my $solo = "A quick brown fox jumps over the lazy dog"; dd $solo.comb[3..4].join; # "ui" dd $solo.comb[3..^5].join; # "ui"