x in mylist is better and more readable than x in mylist[:] and your len(x) should be equal to 3. >>> mylist = [[1,2,3],[4,5,6,7],[8,9,10]] >>> for x in mylist: … if len(x)==3: … print x … [1, 2, 3] [8, 9, 10] or if you need more pythonic use list-comprehensions >>> [x for x in … Read more
You could try this: List<Int32> copy = new List<Int32>(original); or if you’re using C# 3 and .NET 3.5, with Linq, you can do this: List<Int32> copy = original.ToList(); I see that this answer is still getting upvotes. Well, here’s a secret for ya: the above answer is still using a foreach. Please don’t upvote this … Read more
You could create a simple utility function that either converts the given value to a float if possible, or returns it as is: def maybe_float(s): try: return float(s) except (ValueError, TypeError): return s orig_list = [‘data’, ’18’, ’17’, ‘0’] the_list = [maybe_float(v) for v in orig_list] And please don’t use names of builtin functions and … Read more
There are two distinct but similar-looking syntaxes involved here, conditional expressions and list comprehension filter clauses. A conditional expression is of the form x if y else z. This syntax isn’t related to list comprehensions. If you want to conditionally include one thing or a different thing in a list comprehension, this is what you … Read more
Although: max(len(w) for w in words) does kind of “read” easier – you’ve got the overhead of a generator. While: len(max(words, key=len)) can optimise away with the key using builtins and since len is normally a very efficient op for strings, is going to be faster…
try to use key with sorted: sorted(_list2,key=_list1.index) for nested list you can use list comphresnion: [sorted(x,key=_lis1.index) for x in _list2]
Just use Counter from collections: from collections import Counter A = [[x,y],[a,b],[c,f],[e,f],[a,b],[x,y]] new_A = map(tuple, A) #must convert to tuple because list is an unhashable type final_count = Counter(new_A) #final output: for i in set(A): print i, “=”, final_count(tuple(i))
“It would seem silly that Python would not have this kind of capability, because if not you wouldn’t be able to redefine any variable passed through a for loop if it is part of a list that is being passed through.” – That’s how most programming languages work. To allow this capability would be bad … Read more
Those two constructs are handled quite differently: >>> import dis >>> def f(): return [] … >>> dis.dis(f) 1 0 BUILD_LIST 0 3 RETURN_VALUE >>> def f(): return list() … >>> dis.dis(f) 1 0 LOAD_GLOBAL 0 (list) 3 CALL_FUNCTION 0 6 RETURN_VALUE >>> The [] form constructs a list using the opcode BUILD_LIST, whereas the … Read more
If you’re using a 32-bit build of Python, you might want to try a 64-bit version. It is possible for a process to address at most 4GB of RAM using 32-bit addresses, but typically (depending on the OS), one gets much less. It sounds like your Python process may be hitting this limit. 64-bit addressing … Read more