Let’s say I have a dictionary with the following contents: old_dict = {‘a’:[0,1,2], ‘b’:[1,2,3]} and I want to obtain a new dictionary where the keys are the values in the old dictionary, and the new values are the keys from the old dictionary, i.e.: new_dict = {0:[‘a’], 1:[‘a’,’b’], 2:[‘a’,’b’], 3:[‘b’]} To perform this task, I’m… Read More Efficient way to develop a dictionary for reverse lookup?
For example: CREATE TABLE users ( id SERIAL PRIMARY KEY, login_id VARCHAR(20) UNIQUE NOT NULL, login_password CHAR(60) NOT NULL, first_name VARCHAR(20), last_name VARCHAR(20), email varchar(100), last_login_at TIMESTAMP DEFAULT NOW() NOT NULL, join_at TIMESTAMP DEFAULT NOW() NOT NULL ); CREATE TABLE todos ( id SERIAL PRIMARY KEY, user_id INTEGER REFERENCES USERS(id) ON DELETE CASCADE, title VARCHAR(500),… Read More Querying one table that references another table's PK, is the other tables index used?
In this project, I am using JPA/Hibernate and I found an interesting annotation called @Index from the javax.persistence package that can help me create an index without writing SQL. However, I don’t know what kind of index the @Index creates, because it does not provide an option for the type of index. I want to… Read More What kind of index can be created when using @Index in javax.persistence package?
I am a beginner in Python and programming in general and currently training with kata on codewars. I sometimes still struggle with syntax and logic of course but I cannot seem to figure out why my solution is not working for the following exercise and need someone to explain to me where my logic is… Read More Python – Delete every other element from a list: Why does my code only work in some cases?
class<- c(‘A’,’B’) var2<- c(1,0) var3 <- c(0,1) df<- data.frame(class,var2,var3) for (i in colnames(df)[2:3]) { #print(i) table(paste0(‘df$’,i), df$class) } results in error ‘all arguments must have the same length’. Also tried putting get(paste0(‘df$’,i)) Is there a way to loop through these columns and tabulate? >Solution : The issue with your code is that because paste0() returns… Read More using table() with for loop
I want to search a value in a 2d array and get the value of the correspondent "pair" in this example i want to search for ‘d’ and get ’14’. I did try with np location with no success and i finished with this crap code, someone else has a smarter solution? ` import numpy… Read More Python np where , variable as array index, tuple
I would like to use a numpy array to index a numpy matrix using the values of the array indicating the columns, and indices indicating the corresponding row numbers.As an example, I have a numpy matrix, a = np.tile(np.arange(1920), (41, 1)) >>> [[0, 1, 2, …, 1919] [0, 1, 2, …, 1919] … [0, 1,… Read More Values in numpy matrix based on an array using index and value of each element
I’m creating a word filter that if index 1 = dog and index 2 = cat, it will return true. What should I put in next index for word? let textContainer = [‘bird’, ‘dog’, ‘cat’, ‘snake’, ‘rabbit’, ‘ox’, ‘sheep’, ‘tiger’]; for (let word of textContainer) { if (word === ‘dog’ && (next index for word)… Read More How to use the next index of an array in a for..of + if condition in Javascript?
I’m new to firebase and I’m currently trying to understand how to properly index frequently updating counters. Let’s say I have a list of articles on a news website. Every article is stored in my collection ‘articles’ and the documents inside have a like counter, a date when it was published and an id to… Read More Indexing frequently updated counters (e.g., likes on a post and timestamps) in Firebase
How to change the values in nested list How to change the values in the list base on the indexes To clarify, I originally have the_list the_list = [[‘a’,’a’,’a’],[‘b’,’b’,’b’],[‘b’,’b’,’b’],[‘c’,’c’,’c’]] However, I would like to change the values in the_list above that have the index/position in the indexA indexA = [(0,2),(1,2),(0,1)] which I would like to… Read More Change the values in the nested list according to the specified index list