Questions tagged [python]
Programming questions are off-topic here. Do not ask questions about how to write code in Python. However, conceptual questions about computer science are more appropriate. See our help center for the scope of this site.
195
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8
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Need help while writing a code about how to acess value of a label which was executed by while loop in tkinter [closed]
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0
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23
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Create a simple Neural Network of n layers in python from scratch with numpy to solve XOR example problem using Batch Gradient Descent
I'm a young programmer that was interested by machine learning. I watched videos and read articles about the theory behind simple neural networks. However, I can't manage to set it up correctly. I've ...
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0
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2
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70
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Why does Python behave so absurdly when dealing with numbers with decimal points?
r1 and r2 both are assigned 0.05 initially. If r1 is incremented by 0.01 in this way "r1 = r1 +0.01" we have 0.060000000000000005 as answer not 0.06.
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0
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0
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84
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Mutation using scrambling, in genetic algorithm, which fails to converge
I have a piece of Python code I would appreciate help with. As the title says, the code will not converge. I reaches 90-95% accuracy after a few generations, but afterwards it becomes stagnant.
Here &...
0
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0
answers
5
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Reproducible research (published papers) about e-commerce or fashion
I am looking for reproducible research (published papers) about e-commerce and/or fashion which deals with exploratory data analysis, hypothesis testing and regression or ANOVA. This reproducible ...
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0
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3
answers
51
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Number of islands
In the counting number of islands problem, I noticed that one of the solution from internet is as follows
...
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0
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12
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Python | Normalized Vector Based Player Controller
I recently started writing a 3D Engine using the Math Library, and PyGame for Graphics. I've made a simple demo scene, but I would like to make a "First-Person" like Camera Controller.
I've ...
0
votes
1
answer
27
views
Discarding lists of same elements
Suppose, I have a list of lists where multiple lists can have same elements. In my final output, I just want one list with the same element. An example is the following:
Input: A=[[1,2,0], [0,1,2], [2,...
0
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2
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65
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Speeding up an array search for duplicate
I was tasked with writing a function that finds the value of an element that is the first duplicate in an array to be encountered. For the array
[2, 1, 3, 5, 3, 2]
...
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0
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1
answer
39
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Can somebody explain to me the concept of mutability with respect to a NumPy array?
From the NumPy documentation:
"NumPy arrays have a fixed size at creation, unlike Python lists (which can grow dynamically). Changing the size of an ndarray will create a new array and delete ...
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9
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4
answers
2k
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Does an algorithm's space complexity include input?
Consider the Kadane's algorithm for finding maximum subarray within an array:
...
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1
answer
20
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How sparsity term in loss function for sparse autoencoder is making hidden units inactive?
I am working on a Sparse Autoencoder but Andrew NG's notes are hard to understand.
My question is about the following equation: Loss Function.
In sparse autoencoder, the goal is to inactive some ...
1
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1
answer
33
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Finding all zero sums of length m and checking for zero subsums on an abelian group (generalization of the sub sum problem?)
Let $G$ be an abelian group. We say that $G$ has property $V_n$ if for every $m > n$ and a list $L\subset G$ of $m$ elements s.t. $\sum_{g\in L}g=0$ there is a proper subset $\emptyset\neq L'\...
1
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1
answer
49
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Having a 2D matrix with three typed elements, how to efficiently cover one of the types and NOT cover the other one?
I have a matrix with three possible elements: A, B and C. The size of the matrix could be a maximum of 15x16.
$$
\begin{bmatrix}
A & A & C & A\\
A & C & B & C\\
A & C & ...
- 111
1
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1
answer
91
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How can I convert the pseudo-code that solves maximum subarray problem to Python code?
I'm reading Algorithm Design and Application, by Michael T. Goodrich and Robert Tamassia, and sometimes the pseudo-code in this book doesn't make sense at all.
At chapter one they show us 3 solutions ...
- 135
0
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1
answer
67
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Finding whether a point lies on the boundary of an geometrical object or not?
Suppose I have the mesh of an geometrical object (Interval in 1d, Region in 2d, Volume in 3d). How can I find out whether a point lies on its boundary or not?
I am looking for algorithms with ...
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0
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1
answer
70
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Design an algorithm to calculate stock prices on a given day
Given a list of lists containing tuples in sorted(by day) order find and print the total number of stock units owned for every day that occurs at least once.
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0
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19
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Intensity dependent erosion
Let’s say you have an image in the form of an 2D numpy array in python as the one below. Now you want to eroded the image. HOWEVER, you don’t want to erode it equally. It should be eroeded only if the ...
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0
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0
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17
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Determine if a tree is connected from top to bottom
Consider the following scenario: you have a "tree", and it got many levels, each fill with nodes. nodes could only connect to other nodes that is one level above or below it. the connection ...
2
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4
answers
104
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Algorithm that finds 4 "O"s or 4 "X"s on a diagonal, horizontal, or vertical
My algorithm homework revolves around matching 4 "O"'s or 4 "X"'s on a diagonal, horizontal, or vertical. ...
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0
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15
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Is there a python library for generating a mass-spring model?
Given a 3D representation like mesh or point cloud, I want to generate a mass-spring model of it. By mass-spring model I mean this.
Is there a python library for doing this?
1
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2
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265
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Is the complexity of this two-sum binary search algorithm $O(\lg n)$ or $O((\lg n)^2)$?
This algorithm solves the Two-Sum problem$^1$ assuming that the input array/list is sorted.
...
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1
vote
0
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24
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Long and short memory in reinforcement learning Connect 4 AI
I'm writing an AI based on reinforcement learning to play Connect 4. That's my second bot and attempt to RNN and AI (first was copy a code of snake RNN AI from youtube) and I'm looking for some ...
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0
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1
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169
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Finding a Hamiltonian Cycle in a directed graph - graph problem
$N$ towns are given, which we can get to by passing through the northern and southern gates. If you enter a town through a gate, you have to use another gate to leave the town. The merchant would like ...
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3
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2
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468
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Number of Inversions found in Selection sort vs Exchange sort
Exchange sort is similar to selection sort, just swaps "overly eagerly" instead of finding the minimum and doing only one swap. And the swaps affect how often the ...
- 483
0
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2
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891
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Dynamic Programming - Difficult Jumping Frog Problem
Given a set of $n$ stones, arranged in a row at equal distances from each other. The stones are numbered from $0$ to $n-1$. A frog that is on stone number $0$ has to get to stone number $n-1$.
A jump ...
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1
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421
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Implementing Flajolet–Martin algorithm in Python
I am stuck on what to do.
I am trying to create a simple implementation of the Flajolet–Martin algorithm using Python. The stream will be the contents of a text file and you will produce an ...
0
votes
1
answer
147
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Is it faster to use Counting Sort to lexicographically sort characters in a word in Python?
Assuming I have very long words, is it worth it to use Counting Sort with its memory overhead to achieve linear time complexity?
I wrote a Python function that sorts the characters in a given string ...
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0
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176
views
render = font.render(text, 1, (0, 0, 0)) pygame.error: Library not initialized
the error im receiving is : file "/home/lucas/python/cargame/utils.py", line 17, in blit_text_center
render = font.render(text, 1, (0, 0, 0))
pygame.error: Library not initialized
the ...
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3
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1
answer
125
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Using pre-,post-, and in-order indexes to find information about a Binary Search Tree
Recently I have been studying ways of traversing a BST (in python), and have collided with the terms pre-order, post-order and in-order.
I believe that I understood the three terms pretty well, and ...
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2
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2
answers
642
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Doubt about computing running time / time complexity of a function in Python
I am learning about time complexity now, and I am working with BST (Binary Search Trees).
This question needs some context and this is a follow up post to this post. Basically, I would like to compute ...
- 189
2
votes
1
answer
62
views
Which approach of mine for an algorithm upper bound is correct?
Say we have this algorithm in Python.
...
1
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1
answer
126
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When to stop training a back propagation algorithm based on the MSE?
I have a fully connected neural network that consists of 3 inputs + bias, 4 neuron hidden layer, and 2 layer output, I am using the sigmoid activation function on the hidden layer only and use the ...
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1
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0
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28
views
What Data Structure works best for this problem?
I have 2 sets of atmost 25000 4-tuples. Currently, I am storing them as 2 lists of 4-tuples A and B.
I have to perform the following computation for each of the combinations of A and B.
...
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1
vote
2
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187
views
Find the spanning tree minimizing the backtracking in an unweighted graph
I am working with undirected unweighted graphs, and I am searching for an algorithm that gives me a spanning tree minimizing the number of moves to visit every nodes.
For example, given this graph :
...
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1
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0
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23
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Multimodal machine learning dataset fine tuning for binary classification problem
Hello i am new to machine learning, i am working on a multimodal dataset, basically memes dataset, The data consists of an image and an overlay text, i have no clue how to feed a model both of the ...
0
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0
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36
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Why is Python erasing all data in my text file?
I am having trouble understanding what's going on. I have just been introduced to the open() and close() commands in Python. I have a code that is very similar to the code below:
...
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1
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1
answer
174
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Efficient sorting an array generated from random distribution
I need to sort an array of n real numbers that was randomly generated in this way:
I have a given set of k closed intervals: [a1,b1],[a2,b2],...,[ak,bk] whose beginning and end are natural numbers. ...
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-4
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1
answer
171
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Creating a PDA that accepts the following language
Using automata-lib 5.0.0 (Python library), I need help creating a Python program that simulates a PDA that only accepts the following language:
L = {a^m b^n | 0 ≤ m != n}
If you could provide any ...
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0
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0
answers
22
views
Different results in standard deviation of test set and cross validation
I have used KNN for predicting the output power of solar panels. The results are shown below:
Test Set:
MAE = 0.044
MSE = 0.004
Standard Deviation = 0.272
...
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1
vote
1
answer
70
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MAE greater than MSE - is it possible?
I have used KNN for predicting the output power of solar panels. I have done feature scaling based on normalization for all data points. The problem is that the MAE is equal to 0.08, and MSE is equal ...
- 41
1
vote
1
answer
24
views
Is it really impossible to use K-fold cross validation for time series data?
I would like to know if it is impossible to use K-fold cross-validation for time series of data. It has been discussed that it is not reasonable to predict past from future, but I think this does not ...
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1
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1
answer
40
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Machine learning and test split for time series data
I have used different machine learning algorithms to predict solar panels' power output. There are ten independent features for weather data.
In all models, I set time as an index and have used the ...
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2
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185
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Is Python truly OOP?
My understanding is that a programming language is generally paradigm (functional, procedural, OOP) independent: we can code using different paradigms in some language. However, some languages, like ...
0
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1
answer
26
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Scale a vector until it reaches a certain bound
I got a two points A and B with their respective x and y coordinates. Point B determines the direction of the vector AB, and I know that -10^9 <= x,y <= 10^9. ...
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4
votes
1
answer
656
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What are the fundamentals of calculating space complexity in loops?
Imagine you loop n times, and every iteration you create a string of space n with scope only within that iteration (thus it is no longer accessible in the next iteration). I would look and say that I ...
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0
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245
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Python closest subset sum function
I'm writing a closestSubset(s,A) function that takes an integer s and an array of positive integers A and returns an array consisting of elements of A which add up to s. If there is no subset that ...
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4
votes
1
answer
158
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Warnsdorff's rule: more errors with odd sized boards
I wrote an algorithm based on the Warnsdorff's rule to solve the knight's tour problem, where you need to create a sequence of moves of a knight on a chessboard such that the knight visits every ...
- 167
0
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1
answer
45
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Expected value of the remainder when a random variable is divided by a number
Let $a,b,c,d,e,f$ be integers selected from the set $\{1,2,\cdots, 100\}$ uniformly and at random with replacement. Let $M=a+2b+4c+8d+16e+32f$. What is the expected value of the remainder when $M$ is ...
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2
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241
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Why does python's threading library use OS level threads when it can't achieve parallelism?
I was surprised to hear that the threading module from python uses OS level threads. From what I know, OS level threads are more expensive (but can achieve parallelism) meanwhile green threads are ...
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