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问题 I know that the answer to "how to change names in a list of data frames" has been answered multiple times. However, I'm stuck trying to generate a function that can take any list as an argument and change all of the column names of all of the data frames in the list. I am working with a large number of .csv files, all of which will have the same 3 column names. I'm importing the files in groups as follows: # Get a group of drying data data files, remove 1st column files <- list.files('Mang

问题 This question already has answers here : Dictionary comprehension for swapping keys/values in a dict with multiple equal values (3 answers) Closed 10 months ago . I have a dictionary that I want to group by the common values: init_dict = {'00001': 'string1', '00002': 'string2', '00003': 'string1', '00004': 'string3', '00005': 'string2'} I want to create a new dictionary that groups the values and lists the keys like this: new_dict = {'string1': ['00001', '00003'], 'string2':['00002', '00004']

问题 For a named, nested list, what is the best way to extract a specific element? If I have a list with known fields (eg, from a yaml file), I want to extract an element (list or otherwise) without having to search through the names and indices or trying to keep track of the levels in the str output. For example, I know that lm returns a nested list which contains qr info. fit <- lm(mpg ~ wt, mtcars) fit$qr$qraux # [1] 1.176777 1.046354 But if I don't know the order, I just want to specify the

问题 I'm trying to elementwise & and elementwise | 2 lists of 8 lists of 6 binary digits, and it is working very oddly. c1 and c2 start as tuples of length 8 with elements that are tuples of length 6, and res starts out as a list version of c1. anding: for x in range(8): for y in range(6): res[x][y] = (c1[:][x][y])*(c2[:][x][y]) oring: for x in range(8): for y in range(6): res[x][y] = int(c1[:][x][y] or c2[:][x][y]) An example: c1: ((1, 0, 0, 0, 1, 1), (1, 1, 0, 0, 0, 1), (1, 1, 1, 0, 0, 0), (0, 1

问题 I have a list of instances from the same class, and I want to make my list distinct based on a property in the class. What is the most pythonic way to achieve this? Here is some sample code: #!/usr/bin/python #-*- coding:utf-8 -*- class MyClass(object): def __init__(self, classId, tag): self.classId = classId self.tag = tag myList = [] myInstance1 = MyClass(1, "ABC") myInstance2 = MyClass(2, "DEF") myInstance3 = MyClass(3, "DEF") myList.append(myInstance1) myList.append(myInstance3) # note

问题 I have a list of instances from the same class, and I want to make my list distinct based on a property in the class. What is the most pythonic way to achieve this? Here is some sample code: #!/usr/bin/python #-*- coding:utf-8 -*- class MyClass(object): def __init__(self, classId, tag): self.classId = classId self.tag = tag myList = [] myInstance1 = MyClass(1, "ABC") myInstance2 = MyClass(2, "DEF") myInstance3 = MyClass(3, "DEF") myList.append(myInstance1) myList.append(myInstance3) # note

问题 I have a Dictionary, where items are (for example): "A", 4 "B", 44 "bye", 56 "C", 99 "D", 46 "6672", 0 And I have a List: "A" "C" "D" I want to remove from my dictionary all the elements whose keys are not in my list, and at the end my dictionary will be: "A", 4 "C", 99 "D", 46 How can I do? 回答1: It's simpler to construct new Dictionary to contain elements that are in the list: List<string> keysToInclude = new List<string> {"A", "B", "C"}; var newDict = myDictionary .Where(kvp=>keysToInclude

问题 I'm very new to Haskell, and I have a simple question. What function can I use with a and b that will result in a, b times. Example: a = 4 | b = 3 Would return: [4, 4, 4] Thanks! 回答1: replicate : replicate 3 4 will be: [4,4,4] When you know what's the type of the function you need (in this case it was quite obvious that the function you needed had a type similar to Int -> a -> [a] ) you can use Hoogle in order to find it. 回答2: You could also use recursion (although the solutions above should

问题 I have a list x = [90, 100, 121, 123, 88]. These values in the list are frequencies of occurrence of an event in 5 different trials. I am looking to create a histogram from this list. I simply tried: plt.hist(x) plt.show() I get this: I need something like this: Note: Very New to Python. And still learning when and how to use Stackoverflow. 回答1: Since the list x contains the frequencies then use a bar plot: x = [90, 100, 121, 123, 88] plt.bar(range(1,6), x) plt.ylabel('frequency') plt.show()

问题 This question already has answers here : How can I reverse a list in Python? (33 answers) Closed 5 years ago . I was wondering how to reverse a list of lists in python. For example, Original: list = [[1,2,3],[4,5,6],[7,8,9]] Output: new_list = [[7,8,9],[4,5,6],[1,2,3]] Right now, I am trying this: new_list = reversed(list) However, this doesn't seem to work. 回答1: In [24]: L = [[1,2,3],[4,5,6],[7,8,9]] In [25]: L[::-1] Out[25]: [[7, 8, 9], [4, 5, 6], [1, 2, 3]] 来源： https://stackoverflow.com