Sometimes you want to filter a Stream with more than one condition: myList.stream().filter(x -> x.size() > 10).filter(x -> x.isCool()) … or you could do the same with a complex condition and a single filter: myList.stream().filter(x -> x.size() > 10 && x -> x.isCool()) … My guess is that the second approach has better performance characteristics, … Read more
filter, map, and reduce work perfectly in Python 2. Here is an example: >>> def f(x): return x % 2 != 0 and x % 3 != 0 >>> filter(f, range(2, 25)) [5, 7, 11, 13, 17, 19, 23] >>> def cube(x): return x*x*x >>> map(cube, range(1, 11)) [1, 8, 27, 64, 125, 216, 343, … Read more
Implementing a file upload under html is fairly simple, but I just noticed that there is an ‘accept’ attribute that can be added to the <input type=”file” …> tag. Is this attribute useful as a way of limiting file uploads to images, etc? What is the best way to use it? Alternatively, is there a … Read more
When I need to filter a data.frame, i.e., extract rows that meet certain conditions, I prefer to use the subset function: subset(airquality, Month == 8 & Temp > 90) Rather than the [ function: airquality[airquality$Month == 8 & airquality$Temp > 90, ] There are two main reasons for my preference: I find the code reads … Read more
Let’s say I have an object: { item1: { key: ‘sdfd’, value:’sdfd’ }, item2: { key: ‘sdfd’, value:’sdfd’ }, item3: { key: ‘sdfd’, value:’sdfd’ } } I want to create another object by filtering the object above so I have something like. { item1: { key: ‘sdfd’, value:’sdfd’ }, item3: { key: ‘sdfd’, value:’sdfd’ } … Read more
I have first_name, last_name & alias (optional) which I need to search for. So, I need a query to give me all the names that have an alias set. Only if I could do: Name.objects.filter(alias!=””) So, what is the equivalent to the above? 9 s 9 You could do this: Name.objects.exclude(alias__isnull=True) If you need to … Read more
I want to filter a java.util.Collection based on a predicate. 29 s 29 Java 8 (2014) solves this problem using streams and lambdas in one line of code: List<Person> beerDrinkers = persons.stream() .filter(p -> p.getAge() > 16).collect(Collectors.toList()); Here’s a tutorial. Use Collection#removeIf to modify the collection in place. (Notice: In this case, the predicate will … Read more
I’d like to remove the lines in this data frame that: a) contain NAs across all columns. Below is my example data frame. gene hsap mmul mmus rnor cfam 1 ENSG00000208234 0 NA NA NA NA 2 ENSG00000199674 0 2 2 2 2 3 ENSG00000221622 0 NA NA NA NA 4 ENSG00000207604 0 NA NA … Read more
I have a list that I want to filter by an attribute of the items. Which of the following is preferred (readability, performance, other reasons)? xs = [x for x in xs if x.attribute == value] xs = filter(lambda x: x.attribute == value, xs) 15 s 15 It is strange how much beauty varies for … Read more
