tuples

问题 I understand that Swift's tuples serve, for example, as a simple way for a function to return multiple values. However, beyond this "simplicity aspect", I don't see very well any necessity of using tuples instead of structs. Therefore, my question: in terms of design, is there any scenario where tuples are clearly a better choice than structs? 回答1: This question of a slightly "discussion" nature, but I'll add two points in favour of sometimes preferring tuples over structures. Native

问题 I came across a question that states Consider the following relation schema pertaining to a students database: Student ( rollno , name, address) Enroll ( rollno, courseno , coursename) where the primary keys are shown underlined. The number of tuples in the Student and Enroll tables are 120 and 8 respectively. What are the maximum and minimum number of tuples that can be present in (Student * Enroll), where '*' denotes natural join ? I have seen several solutions on Internet like this or this

问题 I came across a question that states Consider the following relation schema pertaining to a students database: Student ( rollno , name, address) Enroll ( rollno, courseno , coursename) where the primary keys are shown underlined. The number of tuples in the Student and Enroll tables are 120 and 8 respectively. What are the maximum and minimum number of tuples that can be present in (Student * Enroll), where '*' denotes natural join ? I have seen several solutions on Internet like this or this

问题 I came across a question that states Consider the following relation schema pertaining to a students database: Student ( rollno , name, address) Enroll ( rollno, courseno , coursename) where the primary keys are shown underlined. The number of tuples in the Student and Enroll tables are 120 and 8 respectively. What are the maximum and minimum number of tuples that can be present in (Student * Enroll), where '*' denotes natural join ? I have seen several solutions on Internet like this or this

问题 I have a dictionary as :- { (1, 1): 16, (1, 2): 16, (1, 3): 16, (1, 4): 16, (2, 1): 24, (2, 2): 24, (2, 3): 24, (2, 4): 24 } ...i want it to be ordered as per tuple key's second field as well as dictionary's value field... so result dictionary should be :- { (2, 1): 24, (2, 2): 24, (2, 3): 24, (2, 4): 24, (1, 1): 16, (1, 2): 16, (1, 3): 16, (1, 4): 16 } ... i tried sorting it with value alone but it messes the keys tuple order.... yes so i assigned it to a list afterwards by doing ... list =

问题 I need to create a list with different datatypes element, for example: {{10, 10}, "IT", 1, "Test", {100, 100}, "Test"} respectively: {object, string, integer, string, object, string} I have tried declaring it as list of objects or using Tuple(Of Object, String, Integer, String, Object, String) but when I give them the values, "Array initializer has too few dimensions" error occurs. The class where the variable is declared: Public Class SignatureResponse Public signature As Tuple(Of Object,

问题 >>> a = (1,2) >>> a += (3,4) >>> a (1, 2, 3, 4) >>> and with a list: >>> b = [1,2] >>> b += [3,4] >>> b [1, 2, 3, 4] >>> As a tuple is immutable and list is mutable, how can we explain the behaviour? 回答1: Tuple is of immutable type, means that you cannot change the values stored in the variable a . For example, doing the following >>> a = (1, 2) >>> a[0] = 3 throws up the error TypeError: 'tuple' object does not support item assignment . On the other hand, for a list, >>> a = [1, 2] >>> a[0]

问题 In python, I wish to sort tuples based on the value of their last element. For example, i have a tuple like the one below. tuples = [(2,3),(5,7),(4,3,1),(6,3,5),(6,2),(8,9)] which after sort I wish to be in this format. tuples = [(4,3,1),(6,2),(2,3),(6,3,5),(5,7),(8,9)] How do i get to doing that? 回答1: Povide list.sort with an appropriate key function that returns the last element of a tuple: tuples.sort(key=lambda x: x[-1]) 回答2: You can use: from operator import itemgetter tuples = sorted

问题 How can I improve the speed of my algorithm, even by the slightest amount. For the reason I made this I don't actually care about speed in the slightest, but I'm wondering what I could change if I did. Even more than pointing out specific things to change, what I really want to know is how you know that there's a more efficient way and how that way works. Basically, what is the track to follow if you want to learn how the low level stuff works so that you can write better code at the higher

问题 If there's a dictionary: test_dict = { 'a':1,'b':2,'c':3,'d':4} I want to find pairs of keys in list of tuples like: [('a','b'),('a','c'),('a','d'),('b','c'),('b','d'),('c','d')] I tried with the following double iteration test_dict = { 'a':1,'b':2,'c':3,'d':4} result = [] for first_key in test_dict: for second_key in test_dict: if first_key != second_key: pair = (first_key,second_key) result.append(pair) But it's generating the following result [('a', 'c'), ('a', 'b'), ('a', 'd'), ('c', 'a')