Simply casting to List<TestB> almost works; but it doesn’t work because you can’t cast a generic type of one parameter to another. However, you can cast through an intermediate wildcard type and it will be allowed (since you can cast to and from wildcard types, just with an unchecked warning): List<TestB> variable = (List<TestB>)(List<?>) collectionOfListA;
Use Except: var firstNotSecond = list1.Except(list2).ToList(); var secondNotFirst = list2.Except(list1).ToList(); I suspect there are approaches which would actually be marginally faster than this, but even this will be vastly faster than your O(N * M) approach. If you want to combine these, you could create a method with the above and then a return statement: … Read more
len() >>> someList=[] >>> print len(someList) 0
You can use the DataFrame constructor with lists created by to_list: import pandas as pd d1 = {‘teams’: [[‘SF’, ‘NYG’],[‘SF’, ‘NYG’],[‘SF’, ‘NYG’], [‘SF’, ‘NYG’],[‘SF’, ‘NYG’],[‘SF’, ‘NYG’],[‘SF’, ‘NYG’]]} df2 = pd.DataFrame(d1) print (df2) teams 0 [SF, NYG] 1 [SF, NYG] 2 [SF, NYG] 3 [SF, NYG] 4 [SF, NYG] 5 [SF, NYG] 6 [SF, NYG] df2[[‘team1′,’team2’]] … Read more
>>> L = [0, 23, 234, 89, None, 0, 35, 9] >>> [x for x in L if x is not None] [0, 23, 234, 89, 0, 35, 9] Just for fun, here’s how you can adapt filter to do this without using a lambda, (I wouldn’t recommend this code – it’s just for scientific … Read more
Here is how you would do this with a nested list comprehension: [[float(y) for y in x] for x in l] This would give you a list of lists, similar to what you started with except with floats instead of strings. If you want one flat list then you would use [float(y) for x in … Read more
I would suggest to use this extension method to chunk the source list to the sub-lists by specified chunk size: /// <summary> /// Helper methods for the lists. /// </summary> public static class ListExtensions { public static List<List<T>> ChunkBy<T>(this List<T> source, int chunkSize) { return source .Select((x, i) => new { Index = i, Value … Read more
The only difference on a bytecode level is that the .extend way involves a function call, which is slightly more expensive in Python than the INPLACE_ADD. It’s really nothing you should be worrying about, unless you’re performing this operation billions of times. It is likely, however, that the bottleneck would lie some place else.
Yes, the order of elements in JSON arrays is preserved. From RFC 7159 -The JavaScript Object Notation (JSON) Data Interchange Format (emphasis mine): An object is an unordered collection of zero or more name/value pairs, where a name is a string and a value is a string, number, boolean, null, object, or array. An array … Read more
Use map with operator.add: >>> from operator import add >>> list( map(add, list1, list2) ) [5, 7, 9] or zip with a list comprehension: >>> [sum(x) for x in zip(list1, list2)] [5, 7, 9] Timing comparisons: >>> list2 = [4, 5, 6]*10**5 >>> list1 = [1, 2, 3]*10**5 >>> %timeit from operator import add;map(add, list1, … Read more