In a Python list comprehension, if else goes before the for, and a bare if goes after it. Get that backwards and Python raises a SyntaxError. The first one labels every item. The second one throws items away. That single difference is what most of the questions about this are really about. I ran each … Read more >>
To save a Matplotlib chart with a transparent background, pass transparent=True to savefig: That clears the figure background and the axes background in the saved file. It changes nothing on screen, which is why people think it didn’t work. Below I check every claim by reading the alpha channel back out of the saved PNG, … Read more >>
torch.cat joins a sequence of tensors along a dimension that already exists. The shapes have to match everywhere except that one dimension, and the result never gains an axis. That last part is the entire difference between torch.cat and torch.stack, which does add an axis. The runs below are on PyTorch 2.14.0 on Python 3.12.5, … Read more >>
A React component not rendering is almost never a React bug. In the great majority of cases it is one of a handful of ordinary mistakes: the tag starts with a lower-case letter, the function forgot its return, the import does not match the export, && put a 0 on the page instead of your … Read more >>
A data grid is a table that sorts, filters, paginates and selects rows for you. In React the usual choice is MUI X DataGrid, whose Community version is free and MIT licensed, and this guide builds a working grid with it: columns, pagination, sorting, checkbox selection, formatted and custom cells. It also answers the question … Read more >>
To use a React error boundary with functional components, you still need one class: React has no hook that catches rendering errors, so the boundary itself has to be a class component even in an app made entirely of function components. You write that class once and wrap your function components in it. The usual … Read more >>
To merge two arrays in TypeScript, use concat() or spread syntax: a.concat(b) and […a, …b] both return a new array and leave the originals alone. That is all you need when the rows are independent. When both arrays hold objects that describe the same records, you usually want one row per id instead of two, … Read more >>
To initialize an array in TypeScript, declare the element type and give it a value: const cities: string[] = [“Austin”, “Denver”], or const ids: string[] = [] to start empty. Array<string> means the same as string[]. For a fixed number of slots use Array.from({ length: n }, …) rather than new Array(n), which leaves holes. … Read more >>
To check if an array is null or empty in TypeScript, write if (!items || items.length === 0), or the shorter if (!items?.length), which covers null, undefined and [] in one test. The order matters: reading .length before the null check throws at runtime. This guide shows both forms running against all four cases, the … Read more >>
To find the maximum value in an array of objects in TypeScript, decide first what you want back. For just the number, map the property and use Math.max(): Math.max(…employees.map(e => e.salary)). For the whole object that holds it, use reduce() and keep whichever item is larger. Both are one line, and both have an edge … Read more >>