# Tagged Questions

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### Project Euler #10 - summation of primes

(From Project Euler) The sum of the primes below 10 is 2 + 3 + 5 + 7 = 17. Find the sum of all the primes below two million. Can someone please help me improve this code? ...
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### Speeding up prime factorization

I have written the following code for returning the list of prime factors. Any speed-enhancing suggestions? ...
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### Custom module of common functions

I got sick and tired of writing certain functions over and over again, so I made a module that has those functions whenever I need them. I don't use it for code I plan on sharing, so I don't need to ...
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### Is_prime check in Python: can this be more pythonic?

I have the following function that checks if a number is prime: ...
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### Sieve of Atkins algorithm

I got the inspiration to write this algorithm from this question. The OP cited the Sieve of Atkin as one of the fastest ways to generate primes. So I figured I would give it a try: ...
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### Checking for Prime Numbers [closed]

def is_prime(n): if n % 2 == 0 and n > 2: return False return all(n % i for i in xrange(3, int(math.sqrt(n)) + 1, 2)) The code works fine for a ...
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### Sieve of Eratosthenes - Standard and Optimized implementation

I am a Java developer who is taking Python for the first time. I'm sure this is not at all elegant since I am thinking more in C syntax. ...
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### Project Euler 27 - Quadratic Primes

Project Euler problem 27 I decided to try simple brute force, and it worked surprisingly quickly. How can this be optimized? ...
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### Prime generator program SPOJ time limit exceed

Problem Statement Input The input begins with the number t of test cases in a single line (t<=10). In each of the next t lines there are two numbers m and n (1 <= m <= n <= ...
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### Count distinct primes, discarding palindromes, in under 2 seconds

Problem Statement Generate as many distinct primes P such that reverse (P) is also prime and is not equal to P. Output: Print per line one integer( ≤ 1015 ). Don't print more than ...
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### Tonelli-Shanks algorithm implementation of prime modular square root

I did an implementation of the Tonelli-Shanks algorithm as defined on Wikipedia. I put it here for review and sharing purpose. Legendre Symbol implementation: ...
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### Sieve of Eratosthenes - Python

I've been doing a lot of Project Euler lately and just wanted to make sure my implementation was as good as it could be. Does anyone have any suggestions on speed this up? ...
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### Strange performance difference

For exercise, I wrote this code: ...
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### Sum of primes program is taking too long

I don't understand what is taking the program so long: ...
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### Summation of primes takes forever

Project Euler Problem 10 asks: "What is the sum of all prime numbers below 2 million?" How do I speed up my code? It's taking forever and I have never gotten the answer. However, I am sure that my ...
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### How Pythonic is my Project Euler #5? (LCM of [1, 2, …, 20])

I have implemented a solution to Project Euler problem 5: 2520 is the smallest number that can be divided by each of the numbers from 1 to 10 without any remainder. What is the smallest positive ...
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### Review my prime factorization function. Is it complete?

This is a function designed to return all the prime factors of a given number, in sorted order from least to greatest, in a list. It relies on another function that checks if a given number is prime. ...
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### Any problems with this prime checker script?

I have just made what seems to me to be the first reliable prime-checking program that works. However, I am not sure if it is completely reliable, or if there are problems. It relies on list-making ...
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### Prime number dictionary

I attempted to write a read-only dictionary, containing primes: ...
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### Attempting to efficiently compute the largest prime factor

As per the help, here's what I'm looking for from this post: best practice and practical advice about (what I think is describable as) buffering the output of a function. So I'm working on the third ...
2k views

### Problem in calculating prime numbers in python [closed]

I'm a noob in programming. I was asked to code a program that can calculate prime numbers. So i coded as provided below. But it prints all the Odd Numbers instead of Prime Numbers. I think the Value ...
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### User-input prime number generator

What do you consider the readability of this program? Do you think it's easy to understand what the variables and functions do just by reading their names? Would you prefer more, less, or this amount ...
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### Efficient way of code reuse for finding the largest prime factor

I was doing timing with variations of function largest_prime_factor. I was able to write a better one largest_prime_factor2. ...
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### better code for generating primes

After considerable effort, I've come up with the following code to generate a list of primes of given length. I would be very interested to see how an experienced coder would modify my code to make it ...
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### Project Euler 407: Is there any more optimal way to solve this idempotent equation (modulo n ring)?

Project Euler problem 407: If we calculate a2 mod 6 for 0 ≤ a ≤ 5 we get: 0, 1, 4, 3, 4, 1. The largest value of a such that a2 mod 6 = a is 4. Let's call M(n) the largest value of a < n ...
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### Calculating all prime palindromes from 0 to 1000 and printing the largest

I have often read about how important clear and efficient code is. Also often people talk and write about 'beautiful' code. Some hints and critic from experienced developers for the following code ...
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### Project Euler #3 - how inefficient is my code?

So I am essentially a complete newbie to programming, and have been attempting to learn Python by completing the Project Euler problems. I haven't gotten very far, and this is my code for problem #3 : ...
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### Returning a list of divisors for a number

This function takes in a number and returns all divisors for that number. list_to_number() is a function used to retrieve a list of prime numbers up to a limit, ...
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### Criticize my first Python module please

This is a Python module I have just finished writing which I plan to use at project Euler. Please let me know how I have done and what I could do to improve it. ...
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### Largest Prime Factor

I'm trying to learn Python by working my way through problems on the Project Euler website. I managed to solve problem #3, which is What is the largest prime factor of the number 600851475143 ? ...
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### Any better way to solve Project Euler Problem #5?

Here's my attempt at Project Euler Problem #5, which is looking quite clumsy when seen the first time. Is there any better way to solve this? Or any built-in library that already does some part of the ...
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### Code review needed for my Prime factorization code

Below is the code for knowing all the prime factors of a number. I think there must be some better way of doing the same thing. Also, please tell me if there are some flaws in my code. ...
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### Functional prime factor generator

I have this prime factor generator for some number n. It returns list of all prime factors. In other words, product of the list equals ...
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### Naive prime finder, unexpected behavior in Python

I have verified that both of my following functions successfully find prime numbers. I was pretty sure the function called is_prime_new would be faster than ...
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### Improving runtime of prime generation

I just answered the question on project euler about finding circular primes below 1 million using python. My solution is below. I was able to reduce the running time of the solution from 9 seconds to ...
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### Prime factorization of a number

I'm trying to learn Python through the excellent online book Dive Into Python 3. I have just finished chapter 2 about data types and felt like trying to write a program on my own. The program takes ...
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### Why is one prime number function hugely faster than another? [closed]

I've found this excellent prime number module file from here as I work through the Project Euler problems, and I'm trying to fully understand the code and the maths behind it. I've come to a hitch on ...
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### Euler 35 - python solution taking too long

Here is my solution for Project Euler 35. (Find the number of circular primes below 1,000,000. Circular meaning all rotations of the digits are prime, i.e. 197, ...