How to make a copy of a 2D array in Python? [duplicate]
Using deepcopy() or copy() is a good solution. For a simple 2D-array case y = [row[:] for row in x]
variable-assignment
Difference between a -= b and a = a – b in Python
Note: using in-place operations on NumPy arrays that share memory in no longer a problem in version 1.13.0 onward (see details here). The two operation will produce the same result. This answer only applies to earlier versions of NumPy. Mutating arrays while they’re being used in computations can lead to unexpected results! In the example … Read more
Why would you use an assignment in a condition?
It’s more useful for loops than if statements. while(var = GetNext()) { …do something with ‘var’ } Which would otherwise have to be written var = GetNext(); while(var) { …do something var = GetNext(); }
Why do C and C++ support memberwise assignment of arrays within structs, but not generally?
Here’s my take on it: The Development of the C Language offers some insight in the evolution of the array type in C: http://cm.bell-labs.com/cm/cs/who/dmr/chist.html I’ll try to outline the array thing: C’s forerunners B and BCPL had no distinct array type, a declaration like: auto V[10] (B) or let V = vec 10 (BCPL) would … Read more
How do I copy the contents of one ArrayList into another?
You can use such trick: myObject = new ArrayList<Object>(myTempObject); or use myObject = (ArrayList<Object>)myTempObject.clone(); You can get some information about clone() method here But you should remember, that all these ways will give you a copy of your List, not all of its elements. So if you change one of the elements in your copied … Read more
Assign variable in while loop condition in Python?
Starting Python 3.8, and the introduction of assignment expressions (PEP 572) (:= operator), it’s now possible to capture the condition value (data.readline()) of the while loop as a variable (line) in order to re-use it within the body of the loop: while line := data.readline(): do_smthg(line)
Can you declare multiple variables at once in Go?
Yes, you can: var a, b, c string a = “foo” fmt.Println(a) You can do something sort of similar for inline assignment, but not quite as convenient: a, b, c := 80, 80, 80
Copy constructor and = operator overload in C++: is a common function possible?
Yes. There are two common options. One – which is generally discouraged – is to call the operator= from the copy constructor explicitly: MyClass(const MyClass& other) { operator=(other); } However, providing a good operator= is a challenge when it comes to dealing with the old state and issues arising from self assignment. Also, all members … Read more
Check if returned value is not null and if so assign it, in one line, with one method call
Same principle as Loki’s answer but shorter. Just keep in mind that shorter doesn’t automatically mean better. dinner = Optional.ofNullable(cage.getChicken()) .orElse(getFreerangeChicken()); Note: This usage of Optional is explicitly discouraged by the architects of the JDK and the designers of the Optional feature. You are allocating a fresh object and immediately throwing it away every time. … Read more
Why does i = i + i give me 0?
Introduction The problem is integer overflow. If it overflows, it goes back to the minimum value and continues from there. If it underflows, it goes back to the maximum value and continues from there. The image below is of an Odometer. I use this to explain overflows. It’s a mechanical overflow but a good example … Read more