tuples

问题 I have the following list of tuples: [('a', 1), ('a', 1), ('b', 1), ('c',1), ('a', 1), ('c', 1)] I would like to know if I can utilize python's reduce function to aggregate them and produce the following output : [('a', 3), ('b', 1), ('c', 2)] Or if there are other ways, I would like to know as well (loop is fine) 回答1: It seems difficult to achieve using reduce , because if both tuples that you "reduce" don't bear the same letter, you cannot compute the result. How to reduce ('a',1) and ('b'

问题 It seems natural to have an std::iterator for std::tuple . However it is not implemented, so programmers implement there own versions. One is for example found at Jonathan Müller's Blog. Do I overlook something? Is there any reason why there is no "official version" for an tuple_iterator? 回答1: std::tuple is not a container, at least not in the sense of the standard library containers. It cannot be iterated with the usual methods because it holds objects of different types. Standard containers

问题 Not sure it is a correct SQL and would like to work backward converting SQL back to tuple relational calculus to check the correctness. Let's say we come up this query to display the classes where all its requirement classes have been complete by all the participants who finished the introduction. So we have two tables, progress and requirement. where progress: mId (string), cId (string) and requirement: : cId (string), rId (string) all the enrollment are kept in progress and all the

问题 I'm following a couple of Pythone exercises and I'm stumped at this one. # C. sort_last # Given a list of non-empty tuples, return a list sorted in increasing # order by the last element in each tuple. # e.g. [(1, 7), (1, 3), (3, 4, 5), (2, 2)] yields # [(2, 2), (1, 3), (3, 4, 5), (1, 7)] # Hint: use a custom key= function to extract the last element form each tuple. def sort_last(tuples): # +++your code here+++ return What is a Tuple? Do they mean a List of Lists? 回答1: A tuple and a list is

问题 What's the difference between these? I know that their type signatures are different, and that all functions start off normal and have to be .tupled to get their tupled form. What's the advantage of using un-tupled (but non-curried) functions? Especially because it seems to me that passing multiple arguments to a tupled function automagically unpacks them anyway, so by all appearances they are the same. One difference i see is that it forces you to have types for every number of function

问题 I have known for a while that the primary difference between lists and tuples in Python is that lists are mutable and tuples are not. Beyond that and the different methods available to them, I know very little about lists and tuples. Is there any other difference between them? Are there any advantages/disadvantages (aside from immutability) in using a tuple over a list in Python 3? Does one have a faster access time, or have a smaller memory size, or contain more methods, than the other? Are

问题 I have known for a while that the primary difference between lists and tuples in Python is that lists are mutable and tuples are not. Beyond that and the different methods available to them, I know very little about lists and tuples. Is there any other difference between them? Are there any advantages/disadvantages (aside from immutability) in using a tuple over a list in Python 3? Does one have a faster access time, or have a smaller memory size, or contain more methods, than the other? Are

问题 I have an array (dtype=object) with the first column containing tuples of arrays and the second column containing scalars. I want all scalars from the second column where the tuples in the first column equal a certain tuple. Say >>> X array([[(array([ 21.]), array([ 13.])), 0.29452519286647716], [(array([ 25.]), array([ 9.])), 0.9106600600510809], [(array([ 25.]), array([ 13.])), 0.8137344043493814], [(array([ 25.]), array([ 14.])), 0.8143093864975313], [(array([ 25.]), array([ 15.])), 0

问题 I was wondering if anyone can teach me how to do element wise addition on a tuple or list without using zip, numpy arrays, or any of those modules? For example if I have: a = (1,0,0,1) b = (2,1,0,1) how can i get: (3,1,0,2) instead of (1,0,0,1,2,1,0,1) ? 回答1: You can do this using operator.add from operator import add >>>map(add, a, b) [3, 1, 0, 2] In python3 >>>list(map(add, a, b)) 回答2: List comprehensions are really useful: [a[i] + b[i] for i in range(len(a))] 回答3: You can use the map

问题 I was wondering if anyone can teach me how to do element wise addition on a tuple or list without using zip, numpy arrays, or any of those modules? For example if I have: a = (1,0,0,1) b = (2,1,0,1) how can i get: (3,1,0,2) instead of (1,0,0,1,2,1,0,1) ? 回答1: You can do this using operator.add from operator import add >>>map(add, a, b) [3, 1, 0, 2] In python3 >>>list(map(add, a, b)) 回答2: List comprehensions are really useful: [a[i] + b[i] for i in range(len(a))] 回答3: You can use the map