Store functions in list and call them later [duplicate]
Yes, you can do it. If you want to call all functions in the list with a “one liner” you can do the following: results = [f() for f in options]
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Assign a number to each unique value in a list
Without using an external library (check the EDIT for a Pandas solution) you can do it as follows : d = {ni: indi for indi, ni in enumerate(set(names))} numbers = [d[ni] for ni in names] Brief explanation: In the first line, you assign a number to each unique element in your list (stored in the … Read more
Prolog, find minimum in a list
It is common to use a so-called “lagged argument” to benefit from first-argument indexing: list_min([L|Ls], Min) :- list_min(Ls, L, Min). list_min([], Min, Min). list_min([L|Ls], Min0, Min) :- Min1 is min(L, Min0), list_min(Ls, Min1, Min). This pattern is called a fold (from the left), and foldl/4, which is available in recent SWI versions, lets you write … Read more
How to create a nested dictionary from a list in Python?
This easiest way is to build the dictionary starting from the inside out: tree_dict = {} for key in reversed(tree_list): tree_dict = {key: tree_dict}
Automatically growing lists in Python
Sure it’s possible, you just have to use a subclass of list to do it. class GrowingList(list): def __setitem__(self, index, value): if index >= len(self): self.extend([None]*(index + 1 – len(self))) list.__setitem__(self, index, value) Usage: >>> grow = GrowingList() >>> grow[10] = 4 >>> len(grow) 11 >>> grow [None, None, None, None, None, None, None, None, … Read more
Converting an int array to a String array
int[] nums = {5,1,2,11,3}; //List or Vector Arrays.sort(nums); //Collections.sort() for List,Vector String a=Arrays.toString(nums); //toString the List or Vector String ar[]=a.substring(1,a.length()-1).split(“, “); System.out.println(Arrays.toString(ar)); UPDATE: A shorter version: int[] nums = {-5,1,2,11,3}; Arrays.sort(nums); String[] a=Arrays.toString(nums).split(“[\\[\\]]”)[1].split(“, “); System.out.println(Arrays.toString(a));
readonly keyword does not make a List ReadOnly?
The modifier readonly means that the value cannot be assigned except in the declaration or constructor. It does not mean that the assigned object becomes immutable. If you want your object to be immutable, you must use a type that is immutable. The type ReadOnlyCollection<T> that you mentioned is an example of a immutable collection. … Read more
Grouping a list into lists of n elements in Haskell
A quick search on Hoogle showed that there is no such function. On the other hand, it was replied that there is one in the split package, called chunksOf. However, you can do it on your own group :: Int -> [a] -> [[a]] group _ [] = [] group n l | n > … Read more
Serializing a list of Key/Value pairs to XML
KeyValuePair is not serializable, because it has read-only properties. Here is more information(thanks to Thomas Levesque). For changing the generated name use the [XmlType] attribute. Define your own like this: [Serializable] [XmlType(TypeName=”WhateverNameYouLike”)] public struct KeyValuePair<K, V> { public K Key { get; set; } public V Value { get; set; } }
Why isn’t there an operator[] for a std::list?
Retrieving an element by index is an O(n) operation for linked list, which is what std::list is. So it was decided that providing operator[] would be deceptive, since people would be tempted to actively use it, and then you’d see code like: std::list<int> xs; for (int i = 0; i < xs.size(); ++i) { int … Read more