In this article, you will learn Alphabet pattern programs using Python. Navi Mumbai - 400710. How do you Find the Factors of a Number in a while Loop in Python? - Toppr As expected, the accepted answer is about the same speed as, This is by far the fastest method here for very large numbers. If you don't want to use any libraries, then I think this is the easiest way to do it: While the question says Python (2.7), people may be interested in this simple solution using Numpy. 592), Stack Overflow at WeAreDevelopers World Congress in Berlin, Temporary policy: Generative AI (e.g., ChatGPT) is banned. are prime numbers as they do not have any other factors. Factors Of A Number In Python - PythonForBeginners.com If this answers your question please mark it as answer. divmod(x, y) returns ((x-x%y)/y, x%y), i.e., the quotient and remainder of the division. For Loop for Prime Factors in Python - Stack Overflow This is what I came up with: I also tried a version that uses tricky generator functions: I ran it once to let Python compile it, then ran it under the time(1) command three times and kept the best time. en.wikipedia.org/wiki/Integer_factorization, Improving time to first byte: Q&A with Dana Lawson of Netlify, What its like to be on the Python Steering Council (Ep. This function returns a dictionary where the keys are the prime factors, and the values are the exponents. That is correct. If youre going to use a library, may as well make it the right one: SymPy, as seen in Evgeni Sergeevs answer. Therefore, to avoid this we are taking the loop till sqrt(N). It compute prime factors of a number e.g., for. Prime numbers are the numbers that are divisible by only 1 and themselves. I'm a little surprised I couldn't find a simple implementation for integer prime factorization in the form (p1 ** e1) * (p2 ** e2) , so I decided to write my own. What's the DC of a Devourer's "trap essence" attack? In this program, we will use a while loop. 2)if number is 11, any greater than 6 (number//2+1) can never be its factor. Note that it's not just an off-by-one; for larger numbers it will be off by more. It is an optimized solution because previously we were traversing the loop till the number itself but now we are traversing only till half of N, more precisely till the square root of N. Therefore, its complexity will be reduced and it will work faster than the other two. "Print this diamond" gone beautifully wrong. Your program increases the divisor x, when it divides a, without checking, if x**i (i>1) divides a. Therefore, the if condition if(N/x==x) is used to avoid such situations. Here's my version: The if sq*sq != num: condition is necessary for numbers like 12, where the square root is not an integer, but the floor of the square root is a factor. Incongruencies in splitting of chapters into pesukim. In your output, the last number represent a product of all prime numbers that are more than once a divisor of a. The [i, n/i] for i in range(1, int(sqrt(n)) + 1) if n % i == 0 returns a pair of factors if the remainder when you divide n by the smaller one is zero (it doesn't need to check the larger one too; it just gets that by dividing n by the smaller one.). It outperforms all the other versions I tested, including dansalmo's, Jason Schorn's, oxrock's, agf's, steveha's, and eryksun's solutions, though oxrock's is by far the closest. What's the translation of a "soundalike" in French? Because these numbers are prime numbers. rev2023.7.24.43543. agf's answer is really quite cool. Help? Python Program to find Prime Number - Tutorial Gateway How to find the factors of a number given the prime factorization? Does ECDH on secp256k produce a defined shared secret for two key pairs, or is it implementation defined? The following piece of code returns a sorted list of all the factors without changing run time asymptotic complexity: Idea: Instead of using the list.sort() function to get a sorted list which gives nlog(n) complexity; It is much faster to use list.reverse() on l2 which takes O(n) complexity. Making statements based on opinion; back them up with references or personal experience. Let us see the code for a better understanding. Representability of Goodstein function in PA. Can consciousness simply be a brute fact connected to some physical processes that dont need explanation? The integer portion of the sqrt(10) = 4 therefore range(1, int(sqrt(10))) = [1, 2, 3, 4] and testing up to 4 clearly misses 5. I timed it running 10000 times on all numbers 1-200 and 100 times on all numbers 1-5000. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Combining this fact with agf's excellent solution, I've ended up with this function: However, on small numbers (~ < 100), the extra overhead from this alteration may cause the function to take longer. Learn Python practically Factorial using For Loop and Range In the following example, we shall use Python For Loop to find Factorial. Below is the code used. You may get further performance improvement for large values of, Thanks I must have been staring at this too long. 46 shouldn't be there. Be sure to grab the number larger than sqrt(number_to_factor) for unusual numbers like 99 which has 3*3*11 and floor sqrt(99)+1 == 10. rev2023.7.24.43543. Example Input : 10 Output : 2 5 Factors can be algebraic expressions as well, dividing another expression evenly. Am I in trouble? To understand this example, you should have the knowledge of the following Python programming topics: Note: To find the factors of another number, change the value of num. How to Find Factors of Number using Python - Online Tutorials Library How to find the factors of a number given the prime factorization? This value is assigned to the variable x in print_factors(). We have a lot of numbers such as Prime numbers, composite numbers, etc. Should I trigger a chargeback? If yes, then we will print the counter number as a factor of the number. Is saying "dot com" a valid clue for Codenames? Stopping power diminishing despite good-looking brake pads? What is the smallest audience for a communication that has been deemed capable of defamation? Inside the function, we are initializing the variable x which will be increased in every iteration so that every number between 1 to Math.sqrt(N) would be checked for its divisibility with N. However, we are running a loop only till sqrt(N) because after that the pairs will start repeating themselves. And note that sympy.divisors is not much faster than the accepted solution. How has it impacted your learning journey? Therefore, we are checking the condition up to less than equal to N. If the number x is divisible by N, therefore, it is a factor of N and hence it is printed. Ltd. All rights reserved. Prime Factorisation is the method in which we recursively divide the number with its prime factors to find all the prime factors of the number. 1 Answer Sorted by: 1 Your problem is the algorithm, not so much the Python code. I figure there's something wrong when I assign i=n and then decremented i, is it also affecting n? Is it a concern? In the next line, we have a while loop, and this loop will execute till i is less than or equal to num. 46*2=92. Similarly, prime factors are prime numbers that are also a factor of a number. Outside of the condition, we will write our increment of the counter. If I change the code to build a list instead, it slows down slightly: I believe that the tricky generator functions version is the fastest possible in Python. Find all the numbers less than or equal to the given number. To learn more, see our tips on writing great answers. However, we will be calculating these factors by the prime factorization method. prime factors of a number are always in between 2,(number//2)+1. Each prime number will have only two factors, i.e. Thank you for helping us improve this article. You can get all the factors by simply removing all unnecessary stuff, but that will not guaranty, that the number is prime number: try this one, I added an additional check to see if number is a prime before appending to primefactors list. Python Program to find Factors of a Number - Tutorial Gateway Factors can be algebraic expressions as well, dividing another expression evenly. These numbers can influence the decisions related to our performances and much more. Factorization means breaking a number into smaller numbers which after multiplying gives us the same number again. For example if you 1) take a number 10, any number greater than 6 can never be its factor. But 10 % 3 does not equal 0. Here is an example if you want to use the primes number to go a lot faster. and therefore still very limited in its efficiency (especially for big numbers without small divisors). So for example: This is obviously not the most efficient implementation for one it iterates over the whole set of natural numbers, instead of going straight for the primes but it's good enough for relatively small values, and simple enough that it can be easily understood. The factors of a number can only be present up to that number. "Fleischessende" in German news - Meat-eating people? Finding prime factors of a number using "for loop" in python, Iterating over numbers including prime factors, Problem with Creating a Prime Factor List (Edit: Title should say 'Factor List', not 'Prime Factor List'). If you put int(math.sqrt(n)) + 1 outside of the for loop you should get bit more performance out of it since won't have to re-calc it each iteration of the for loop. If num is divisible by i, then i is a factor of num and we will print the i with a message. Asking for help, clarification, or responding to other answers. I believe I have the first part correct in checking for the factors, but somehow I'm not sure what I'm missing in the second part of checking for prime numbers. Why is the upper limit of the range (number/2)+1 ? Courses & Tutorials for Beginners Programmers, 104, Building No. minimalistic ext4 filesystem without journal and other advanced features, Representability of Goodstein function in PA, "Print this diamond" gone beautifully wrong. python - Sum the factors of a number (excluding the number itself A factor of a number 'n' is the one that divides the number 'n' completely, that is, on dividing 'n' with it, the remainder should be zero. Could ChatGPT etcetera undermine community by making statements less significant for us? In this approach, we check for each number from 1 to N if it divides N, if yes then we print it. 5 Making statements based on opinion; back them up with references or personal experience. and Get Certified. If yes, print out the number. After l2.reverse(), l2 may be appended to l1 to get the sorted list of factors. 592), Stack Overflow at WeAreDevelopers World Congress in Berlin, Temporary policy: Generative AI (e.g., ChatGPT) is banned. Let's explain it with an example. Code Explanation: Factors of a Number in Python Using for Loop In this program, at the very first line, we have accepted a number from the user and converted it into an int, and stored the same number into variable n. In the next line, we have initiated for loop to check factors of numbers. Time Complexity: O(N) Almost all the algorithm here limit to the range to the number * .5, but actually that range is much smaller. Given all the prime factors, all other factors can be built easily. Is this mold/mildew? To find the factors of a number M, we can divide M by numbers from 1 to M. While dividing M, if a number N leaves no remainder, we will say that N is a factor of M. For this purpose, we can use a for loop in python as follows. Python Program to find Prime Factors of a Number - Tutorial Gateway An explanation of how it solves the problem always helps an answer be more useful. Can I opt out of UK Working Time Regulations daily breaks? My bechamel takes over an hour to thicken, what am I doing wrong. I was thinking of prime factorization where you'd want to call out multiple 3's. Python For Loops - W3Schools I was interested in seeing whether, Compared to other answers, this may not be as efficient, since the OP requests for efficiency specifically, @SreenikethanI Totally agree with you. Iterating over numbers including prime factors. Your problem is the algorithm, not so much the Python code. I was pretty surprised when I saw this question that no one used numpy even when numpy is way faster than python loops. 2 These lists are easy to find on the internet. 2, 3, 5, 7 etc. You can then use x / fac1 to get fac2. This will return all of the factors, very quickly, of a number n. sqrt(x) * sqrt(x) = x. Almost all the algorithm here limit to the range to the number * .5, but actually that range is much smaller. Notice that the numbers of the x-axis are not the input to the functions. To learn more, see our tips on writing great answers. Python Program to Find the Factors of a Number - BTech Geeks Can somebody be charged for having another person physically assault someone for them? By the way, sympy.divisors may be a better match to answer this question. No significant difference here, but with bigger numbers, the advantage is obvious: X = range(1,100000,1000) (only odd numbers), X = range(2,100000,100) (only even numbers), X = range(1,100000,1001) (alternating parity). Using one for loop, iterate over the numbers from 1 to n.. Check for each number in the loop if it is a divisor of the given number or not. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. For a given num = 56 my code below outputs [2, 7, 4], whereas the right answer would be [2,2,2,7]. You can pick up a small (2-3%) speed improvement by returning, This does not, it is unecessarily quadratic time. The factorial of zero is one . What would naval warfare look like if Dreadnaughts never came to be? I noticed that you have duplicate code in your if-else block. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Inside the while block, we will check if num is divisible by i which is the counter. Millennium Business Park, Mahape, Release my children from my debts at the time of my death. This will not return 1 nor the number itself n. So it will return an empty array if n is prime. 5, Sector 3, its actually sqrt of the number. Navi Mumbai - 400710, Video Explanation of Factors of a number in Python, Method 1: Factors of a number using for loop in Python, Method 2: Factors of a number using while loop in Python. if we have the lower divisor we can get he upper one easily. Here's an alternative to @agf's solution which implements the same algorithm in a more pythonic style: This solution works in both Python 2 and Python 3 with no imports and is much more readable. I thought of that, but then why does it print out 20 like it says in the question? Here's a link! Python Practice Series. How To Find Factors Of A Number In Python? So where ten is the input would be 2**10-1 = 1023, your max factor is not more than your number, so, let's say. Courses & Tutorials for Beginners Programmers, 104, Building No. Enter a number:15 The factor of 15 are: 1 The factor of 15 are: 3 The factor of 15 are: 5 The factor of 15 are: 15 Code Explanation Method 2: Factors of a number using while loop in Python. Any ideas? Python Program to Find the Factors of a Number using While Loop ; Python Program to Find the Factors of a Number using Functions ; Python Program to Find the Factors of a Number using For Loop . Python program to find factors of a number using for loop and while The formula finds the factorial of any number. To learn more, see our tips on writing great answers. where am I going wrong? # Python program to find the factorial of a number provided by the user. a potentially more efficient algorithm than the ones presented here already (especially if there are small prime factons in n). Finding prime factors of a number using "for loop" in python Step 3: After taking the sum, multiply the exponents together. "Print this diamond" gone beautifully wrong. It uses sum to flatten the list. In this program, we will use a while loop. The reduce(list.__add__, ) is taking the little lists of [fac1, fac2] and joining them together in one long list. A number N can only have factors in the range of 1 to N. Approach: Assume the input is a number N. l2 contains q-s which are decreasing. Since sqrt(16)=4sqrt(16) = 4sqrt(16)=4 and as you can see after 4, the pairs have started repeating themselves as (2x8)(2x8)(2x8) is the same as (8x2)(8x2)(8x2) and (1x16)(1x16)(1x16) is the same as (16x1)(16x1)(16x1). Your answer is clearer, so I was able to grok it just enough to misunderstand. To loop through a set of code a specified number of times, we can use the range () function, The range () function returns a sequence of numbers, starting from 0 by default, and increments by 1 (by default), and ends at a specified number. Python program to find factors of a number using for loop and while loop. By clicking Post Your Answer, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct. Is not listing papers published in predatory journals considered dishonest? Should I trigger a chargeback? All the numbers that are involved in all these products are the factors of the given number. The pairs will be (1x16)(1x16)(1x16), (2x8)(2x8)(2x8), (4x4)(4x4)(4x4), (8x2)(8x2)(8x2), (16x1)(16x1)(16x1). Therefore, we write a program to Find the Factors of a Number in Python Language. There is an industry-strength algorithm in SymPy called factorint: This took under a minute. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. @user2357112, I accidentally deleted that line when I was deleted the comment lines. Can I spin 3753 Cruithne and keep it spinning? Let's understand this code now. since its just the number / divisor. I found a simple solution using cypari library in python. Now, let us see the program to find the factors of a number in Python using for loop. Python: Find the two prime factors of a number. You should have knowledge of the following topics in python programming to understand these programs: In these given programs, we have taken input 60 a random number then applied the for loop and makes a calculation on this random number. Asking for help, clarification, or responding to other answers. while n % factor == 0 and factor < n: This would mean that once n % factor test condition is false, the code will break out of the while loop. However, factorization of a number can be defined as breaking the number into a product of smaller numbers which when multiplied together will give the original number. I know you are getting this topic with enough understanding of factors; I am sure you can crack any interview or solve problems on factors in just seconds. Conclusions from title-drafting and question-content assistance experiments Iterating again, prime factors loop, python, Finding prime factors of a number using "for loop" in python, Program thats asks for a number then prints out all its factors, 150 --> 2,3,5,5, Factors of a number using Python recursive function, Trying to make an efficient way to find all factors in python using for loops, While loop doesn't stop when number is power of 2. for 16 i get 4 for the sqrt, then loop from 1 to 4. since 2 is a lower bound divisor of 16 we take 16 / 2 . For all the practice Videos and Explanations on Python, please click over here. This should be fine, as that is what the OP asked for. Making statements based on opinion; back them up with references or personal experience. Take our 15-min survey to share your experience with ChatGPT. Connect and share knowledge within a single location that is structured and easy to search. Airline refuses to issue proper receipt. prime factors of a number are always in between 2,(number//2)+1. What is the most efficient way to find amicable numbers in python? However, there would be a case left where we need to apply an extra condition for N!=1N!=1N!=1. In this approach, we check for each number from 1 to N if it divides N, if yes then we print it. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Copyright 2020-2023. C Program to Enter Two Numbers and Perform All Arithmetic Operations, Python Program to Calculate Total Marks Percentage and Grade of a Student, GCD of Two Numbers in Python using For loop | Recursion | Function | Euclidean Algorithm, C Program to Find Power of a Number using For | While | Function | Recursion | pow(), String Reverse in Java Program | For | Recursion | Function | StringBuilder | StringBuffer | Stream, Sum of Digits of a Number PHP Program using While loop. Is it better to use swiss pass or rent a car? Was the release of "Barbie" intentionally coordinated to be on the same day as "Oppenheimer"? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Unless I am missing something I would suggest, if you must do it this way, using int(ceil(sqrt(x))). Generalise a logarithmic integral related to Zeta function. But it's not really much faster than the reduce version, roughly 4% faster based on my measurements. Trying to make an efficient way to find all factors in python using for loops, Fast Algorithm to Factorize All Numbers Up to a Given Number, Faster Way To Find Factors of n only using the math library. Here we have for loop having a counter as i and then this loop will start from 1 to the number the user has provided to check the factor plus 1. What is the most efficient way of finding all the factors of a number in Python? A positive integer greater than 1 which has no other factors except 1 and the number itself is called a prime number. You should always indent with 4 spaces in Python. Was the release of "Barbie" intentionally coordinated to be on the same day as "Oppenheimer"? What would naval warfare look like if Dreadnaughts never came to be? I wanted to see if I could rewrite it to avoid using reduce(). for 16 i get 4 for the sqrt, then loop from 1 to 4. since 2 is a lower bound divisor of 16 we take 16 / 2 to get 8. if we have 1 then to get 16 is (16 / 1). Thus it is the result of multiplying the descending series of numbers. The value 4 is repeating itself, but we do not want repetition in our output. In the above, after taking the input, we run a loop from 2 because prime numbers start from 2 and end our loop at math.sqrt(N)+1 as the factors will not be present after reaching half of N. Now, we keep on dividing the value of N until possible with i to find its prime factors and simultaneously print them. This would mean that once n % factor test condition is false, the code will break out of the while loop. What is the smallest audience for a communication that has been deemed capable of defamation? It doesn't find all divisors but only prime factors so it's not really an answer. What's the DC of a Devourer's "trap essence" attack? To find the factors of a number using division: To find the factors using the multiplication: In this program, at the very first line, we have accepted a number from the user and converted it into an int, and stored the same number into variable n. In the next line, we have initiated for loop to check factors of numbers. Thanks for contributing an answer to Stack Overflow! # change the value for a different result num = 7 # To take input from the user #num = int (input ("Enter a number: ")) factorial = 1 # check if the number is negative, positive or zero if num < 0: print("Sorry, factorial does not exist for negative numbers") elif num == 0:. Finding the prime factors of a number in Python 2 Factors of a Number in Python Using for Loop - Newtum In this program, at the very first line, we have accepted a number from the user and converted it into an int, and stored the same number into variable n. In the next line, we have initiated for loop to check factors of numbers. For n = 4, this will return 2 twice, so set gets rid of one of them. `i = 9 -> 99%9 == 0 -> 9 and 99/9=11 is added. Then we have an if condition to check if the counter variable number can fully divide the input number or not. 592), Stack Overflow at WeAreDevelopers World Congress in Berlin, Temporary policy: Generative AI (e.g., ChatGPT) is banned. Find centralized, trusted content and collaborate around the technologies you use most. Using set() makes the code slightly slower, and is only really necessary for when you check the square root. If this answers your question please mark it as answer. What are some compounds that do fluorescence but not phosphorescence, phosphorescence but not fluorescence, and do both? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Detect whether sequence is a multiple of a subsequence in Python. Stopping power diminishing despite good-looking brake pads? Since 10000000000000079 is a prime, the accepted answer's algorithm will never find this factor.