ALL Python Programmers Should Know This!!

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b001

b001

Жыл бұрын

⭐ Join the Byte Club to practice your Python skills! ($2.99/mo): / @b001
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This quick demonstration shows you how powerful Python's filter() function can be!
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Пікірлер: 885
@b001
@b001 Жыл бұрын
Correction: 1 is not prime. My is_prime function is flawed!
@JimMaz
@JimMaz Жыл бұрын
You've made a b001 of yourself
@damian4601
@damian4601 Жыл бұрын
just make nums range(2,1000) to exclude 1 instead of making 999 num!=1 comparison
@careca_3201
@careca_3201 Жыл бұрын
@@damian4601 or just add another condition, because you might want to use 1 in a non prime numbers list
@thefredster55
@thefredster55 Жыл бұрын
Couldn't you just set nums equal to 1000 instead of range(1,1000) since you're passing it into a range in the function? (Genuine question, literal n00b here)
@Killercam1225
@Killercam1225 Жыл бұрын
@@thefredster55 Nope, because it creates an array of numbers in that given range. So the function iterates through each number in the list and and the filter function creates an object, which then he passes the object through the [list] method which puts all of the values contained in that object into a [list] where the output can be comprehended.
@boredd9410
@boredd9410 Жыл бұрын
Minor thing, but you can make the prime checking function faster by going up to floor(sqrt(n)) instead.
@slammy333
@slammy333 Жыл бұрын
Could make it even faster by only iterating over odd numbers as well
@programmertheory
@programmertheory Жыл бұрын
def is_prime(x): if x < 2: return False if x
@darkfireguy
@darkfireguy Жыл бұрын
​@@slammy333 you can make it even faster by only checking n-1 and n+1 where n is each multiple of 6
@sidneydriscoll5579
@sidneydriscoll5579 Жыл бұрын
def isPrime(x): if x == 1: return False if x == 2: return False if x == 3: return True if x == 4: return False This is what you call fast!
@FuzioN2006
@FuzioN2006 Жыл бұрын
Why is a youtube comment thread more productive than my work team... FML
@foxerity
@foxerity Жыл бұрын
my man actually made the least efficient function in the history of functions
@chervilious
@chervilious 9 ай бұрын
Not only that, it's also wrong
@chemma9240
@chemma9240 6 ай бұрын
😂
@rkidy
@rkidy 5 ай бұрын
Crazy that when doing a demonstration you focus on ease of understanding the concept rather than efficient of an algorithm unrelated to what he is demonstrating 🤯🤯🤯
@fruitguy407
@fruitguy407 5 ай бұрын
False, I can and do write worse code with more flaws. You're welcome.
@ImThatGuy000
@ImThatGuy000 4 ай бұрын
im new to python, could you explain why?
@philfernandez835
@philfernandez835 Жыл бұрын
primes = [x for x in range(2, 1000) if isPrime(x)]
@krakenzback7971
@krakenzback7971 Жыл бұрын
yeah cuz 1 is not prime
@BookOfSaints
@BookOfSaints Жыл бұрын
I think his point is to use list comprehension which is the better choice here.
@krakenzback7971
@krakenzback7971 Жыл бұрын
@@BookOfSaints yeah this is list comprehension
@BeasenBear
@BeasenBear 8 ай бұрын
It says "isprime" or "Prime" is not defined when I tried this code. What did I miss?
@ItzMeKarizma
@ItzMeKarizma 5 ай бұрын
@@BeasenBear kinda late but he's calling a function called isPrime and you probably didn't define that function (I don't know if it's supposed to be imported or written by yourself, I use C++).
@aciddev_
@aciddev_ Жыл бұрын
"all python programers should know this: pep-8" when
@yujielee
@yujielee Жыл бұрын
💀💀💀
@feDUP1337
@feDUP1337 Жыл бұрын
So damn true
@Cristobal512
@Cristobal512 Жыл бұрын
What is that?
@vorpal22
@vorpal22 Жыл бұрын
@@Cristobal512 PEP-8 consists of the Python recommended standards and best practices.
@user-cg1ul8bh8w
@user-cg1ul8bh8w 4 ай бұрын
Pep8 is just for jealous and mean programmers..... It just unreadable
@rutabega306
@rutabega306 Жыл бұрын
Okay that time complexity tho
@TheG7
@TheG7 Жыл бұрын
Ikr, it would’ve help to use the root of num but still
@moy92
@moy92 Жыл бұрын
newbie here, how would you improve? i thought list comprehensions but dont know ways improve on time complexity
@rogerab1792
@rogerab1792 Жыл бұрын
​@@moy92 memoization
@rutabega306
@rutabega306 Жыл бұрын
@moy92 There are a few ways you can reduce the time complexity because the one in the video is so suboptimal (quadratic time) You can bring it down to O(Nsqrt(N)) by just checking for factors below the square root. But since we are already collecting a list of primes, we can use some kind of sieve algorithm (look up Sieve of Eratosthones on wikipedia). This will be O(NloglogN) or even less depending on the algorithm.
@TheG7
@TheG7 Жыл бұрын
you don't even need if statements to find prime numbers
@AndrewMycol
@AndrewMycol Жыл бұрын
Even as a junior web developer, I really like how you do these shorts. It concisely and simply explains whats going on in the shorts.
@b001
@b001 Жыл бұрын
Thanks so much! Glad you enjoy!
@originalbinaryhustler3876
@originalbinaryhustler3876 Жыл бұрын
​@@b001 keep these shorts coming ❤❤❤❤
@prouddesk6577
@prouddesk6577 4 ай бұрын
His code is horrible. I am sorry but dont watch this guy.
@Siirxe
@Siirxe Жыл бұрын
You can also do primes = [i for i in list(nums) if is_prime(i)]
@kazzaaz
@kazzaaz Жыл бұрын
this is the way it should be done
@danielf5393
@danielf5393 Жыл бұрын
You don’t need to cast to list (and you shouldn’t if nums is a long generator)
@kazzaaz
@kazzaaz Жыл бұрын
​@@danielf5393 For long inputs or generators, another generator also outperforms map/filter pipeline. gen = (i for i in list(nums) if is_prime(i)) for x in gen: print(x)
@danielf5393
@danielf5393 Жыл бұрын
@@kazzaaz hence prime_generator = ( i for i in nums if is_prime(i) ) I’m complaining about “list(nums)” specifically.
@hrocxvid
@hrocxvid Жыл бұрын
This was the first thing I thought of
@Tomyb15
@Tomyb15 Жыл бұрын
I would use a generator function to generate a (possibly infinite) sequence of primes by keeping a record of all previously found primes and checking if the next number is divisible by any of those (that should all be smaller than the number) in order. Uses a tiny bit more memory but cuts down on a lot of division operations.
@jaserogers997
@jaserogers997 Жыл бұрын
Using a sieve (if you had an upper limit) would be faster than that.
@plaskut
@plaskut 6 ай бұрын
generator with sieve
@OMGclueless
@OMGclueless 2 ай бұрын
@@plaskut It's possible to make an infinite generator with a sieve but it's actually pretty complicated. The sieve by default marks all multiples of a prime the first time you encounter that prime, which is impossible if the generator is infinite. Instead you'd need to suspend and then resume the markings later as you advance through the generator, which is possible but pretty tricky to get right.
@plaskut
@plaskut 2 ай бұрын
@@OMGclueless I think I might try doing this. I believe it's a divergent function, so at some point it might have to check to see if the universe has ended yet.
@ubiabrail6773
@ubiabrail6773 Жыл бұрын
Sieve of Eratosthenes is much better for this , but only if u need nums from 1 sieve works with O(n) in spite of this which works withO(n*sqrt(n))
@vorpal22
@vorpal22 Жыл бұрын
Doesn't this actually run in O(n^2) since for a prime number, he's checking up to n-1 instead of sqrt(n)? Agreed that Sieve of Eratosthenes is the way to go, and it's a really easy algorithm to understand.
@brianhull2407
@brianhull2407 5 ай бұрын
A better is_prime function would be: def is_prime(num): if num == 1 or num == 0: return False for x in range(2, floor(sqrt(num))): if num % n == 0: return False return True This does three things. First, it factors in the fact that 1 is not prime. (It’s neither prime nor composite.) Second, it accounts for the fact that 0 isn’t prime either (as 0 is highly composite, having literally every integer as a factor). And third, it increases the speed of the function since it only needs to go to the square root of the number. This works because every composite number has at least one factor that is greater than 1 and less than or equal to its square root. Indeed, given any integer x such that x > 1, for every factor _a_ of x that is less than √x, there is exactly one other factor _b_ of x that is greater than √x such that _a_ × _b_ = x. (For 1, it has exactly one factor (itself), and its lone factor is also its square root. For 0, it has infinite factors (everything), but its square root (itself) is less than all other whole numbers.) Incidentally, if num is less than 2, then both range(2, num) and range(2, floor(sqrt(num))) will return an empty iterable that will cause the body of the for loop to never be executed. As such, any value for num that is less than 2 will return True for the original version of is_prime, and any value for num that is less than 0, between 0 and 1, or between 1 and 2 will return True for my version of is_prime. We could add a check for nonintegers: if num != floor(num): return False However, that isn’t strictly necessary, since the input should be an integer, and in Python, we assume the developer would not put a fraction into the function. And it’s not like the code would throw an error in such a case, anyways. The better question is with regards to negative numbers. There are four ways to consider this. First, we could just assume that the developer would never input a negative number. This is fine… unless we’re getting input from a user, in which case either the developer or the function should do a check. The second way is to treat all negative numbers as composite on the grounds that they each have at least three factors: 1, itself, and −1 (where we only include −1 as a factor if the number itself is negative), and prime numbers must have exactly 2. In that case, our first conditional would instead be: if num == 1 or num
@themusicremixco
@themusicremixco 4 ай бұрын
As a mathematician, #3 and #4 are the correct options here. Either you're working over positive integers, in which case you should throw an exception if negative, or you are working over all integers, which you can use the general definition of a prime element over a commutative ring: p is prime if p is non zero, p is not a unit (here a unit is 1 or -1), and if p=a*b for a and b integers then either p divides a or p divides b. You can see based on this definition that 6 is not a prime: 6=2*3 but 6 does not divide 2 or 3 evenly (i.e. 2/6 and 3/6 are not integers). Similarly for (-6)=(-2)*3, so -6 is not prime. And for positive primes p, we must have p=(±1)*(±p), and p divides ±p. Similarly, -p=(∓1)*(±p), and -p divides ±p. So p is prime is equivalent to saying -p is prime. Notice that over all integers, all primes p have 4 factors: 1, -1, p, -p. It is incorrect to assume all primes have 2 factors, otherwise the only primes over the integers would be 1 and -1.
@brianhull2407
@brianhull2407 4 ай бұрын
@@themusicremixco Thank you for your input! I was unaware of how primes work under anything other than nonnegative integers, so I wasn’t aware of the “four factor” definition. I figured there probably _was_ something, though. That said, it is worth noting that, in computing, we don’t always want perfect mathematical accuracy. Sometimes, we prefer speed over accuracy.
@salvatorearpino9243
@salvatorearpino9243 Жыл бұрын
I usually prefer the list comprehension method instead of filter ie: [n for n in nums if is_prime(n)]
@arjundureja
@arjundureja Жыл бұрын
List comprehension is also faster since. you don't need to convert it back to a list
@salvatorearpino9243
@salvatorearpino9243 Жыл бұрын
@@codeman99-dev timing performance was pretty similar between the two methods. When you check out the disassembled python bytecode (using the dis module), list comprehension has more operations with the python interpreter, so it will most likely not be preferable for code that uses multiple threads (it's more susceptible to global interpreter lock slowing it down)
@vorpal22
@vorpal22 Жыл бұрын
List comprehensions are faster, and in this case, a generator would be even better. Both map and filter are discouraged in Python 3.
@reef2005
@reef2005 Жыл бұрын
For a relatively large number, the isprime func will take a long time to return true or false. Instead of checking every integer
@alexwhitewood6480
@alexwhitewood6480 Жыл бұрын
Previous primes upto square root of nums*
@reef2005
@reef2005 Жыл бұрын
@@alexwhitewood6480 yes indeed
@stareSimulVelCadere
@stareSimulVelCadere 21 күн бұрын
getting more and more declarative, love it
@wiccanwanderer82
@wiccanwanderer82 Жыл бұрын
You only need to check if it's divisible by smaller primes.
@alpacalord507
@alpacalord507 Жыл бұрын
But than you need to have a list with primes, so this does not really help
@thesnakednake
@thesnakednake Жыл бұрын
@@alpacalord507 You can build the list as you go; if you let the is_prime function take the existing prime list into account, you can just append new primes you find until you reach the end of the range. However, you can only do this when you’re making the list in order from 2 like this, since you wouldn’t have all the prior primes otherwise
@alpacalord507
@alpacalord507 Жыл бұрын
@@thesnakednake And? That's still not solving the problem of checking if a number is prime. You're making a list of primes now, which does not (really) help us checking if a number is prime.
@dfsgjlgsdklgjnmsidrg
@dfsgjlgsdklgjnmsidrg Жыл бұрын
@@alpacalord507 u stupid but your profilpic is meliodas so im not mad
@thesnakednake
@thesnakednake Жыл бұрын
@@alpacalord507 The task in the video is to make a list of the primes from 1 to 1000, not just to check if a number is prime. The function that checks it in this video is a means to an end, not the end goal
@uselessschmuck190
@uselessschmuck190 Жыл бұрын
Dude makes me wanna get programing socks and learn python
@DeepFriedOreoOffline
@DeepFriedOreoOffline 11 ай бұрын
This is really awesome! I was making a program the other day and I kept getting a similar return to the one you show at the end there and had no idea what was going on! Life saver!
@FirstnameLastname-rl4qi
@FirstnameLastname-rl4qi Жыл бұрын
Could be more efficient, when checking for a prime you only have to check for factos up too the square root of the number, so if you square root the high end of the range it should work faster!
@rohakdebnath8985
@rohakdebnath8985 7 ай бұрын
Sieve of Eratostenes where you take a vector bool of all trues, then you start a loop from i²(i = 2 to √N) and flag all the multiples in the vector. The position of the trues left in the vector are all the prime numbers till N. This is simpler shorter and well known.
@AWriterWandering
@AWriterWandering Жыл бұрын
Alternatively, you can use a conditional within a list comprehension: [ n for n in nums if is_prime(n) ]
@HussamHadi
@HussamHadi Жыл бұрын
This is the correct pythonic way of solving it. Avoid using filter whenever possible
@e1ke1k96
@e1ke1k96 Жыл бұрын
Or even : [n for n in nums if n%2==0]
@nullopt5174
@nullopt5174 Жыл бұрын
@@e1ke1k96 that’s not how you define a prime number.
@patrickcuster2348
@patrickcuster2348 Жыл бұрын
The tradeoff is that a list comprehension is going to store the whole list in memory while filter keeps it as a generator until needed. Both are pythonic and have their uses
@AWriterWandering
@AWriterWandering Жыл бұрын
@@patrickcuster2348 yes, but in the video he used to list function, so a list was the intended output anyway.
@unknownman6978
@unknownman6978 Жыл бұрын
we have all of the prime numbers 1, 2, 3 💀💀
@-sn4k3-94
@-sn4k3-94 Жыл бұрын
It’s prime, what’s wrong?
@finnyass1407
@finnyass1407 Жыл бұрын
@@-sn4k3-94 1 isn’t a prime number tho
@asi3136
@asi3136 7 ай бұрын
​@@finnyass1407argument of semantics, it's generally not considered a prime but the arguments are vibes
@t.gmultiplex2838
@t.gmultiplex2838 11 күн бұрын
At every line for a sec I thought he missed; then remembered oh yeah it's python 🤣😂
@back2710
@back2710 11 ай бұрын
For those concerned for its complexity, remember you can always use sieve of eratosthenes in most cases, this only would be required in case of big numbers
@nagyzoli
@nagyzoli 9 ай бұрын
Sieve works for any number, and it is the most optimal way of generating sequences of primes.
@user-th2cp8uh8r
@user-th2cp8uh8r Жыл бұрын
I must admit that I'm a little mad that this didn't show up when I needed it but this tips are very cool and informative!
@user-yj3mf1dk7b
@user-yj3mf1dk7b Жыл бұрын
open book
@davesharp5472
@davesharp5472 Жыл бұрын
Props to you for making videos where you know that 90% of the comments will be “well actually….” Or some other form of telling you how you are wrong and should have done it their way.
@davesharp5472
@davesharp5472 Жыл бұрын
​@Harrod Thou Thanks for chiming in. Id say its more ironic you dont view comments like "Thanks for teaching job applicants to not format their code properly and also use a less readable alternative of list comprehensions." as negative. I'm offering support to b001 and props for sticking his neck out there. This field particularly is filled with people who love nothing more than to correct people, not too dissimilar to your response to me. See Stack Overflow for example. Have a good day.
@zhairewelch8291
@zhairewelch8291 Жыл бұрын
@Harrod Thou the neg comments are there, it just doesn’t take up 90% of the comment section.
@Pharisaeus
@Pharisaeus 10 ай бұрын
Not sure if it's such a great idea. I personally always report such videos, eg. as "misinformation" and choose for them to not be recommended any more.
@BeasenBear
@BeasenBear 8 ай бұрын
I tried your code and it worked! I'll check your channel for more!
@newsjuice7404
@newsjuice7404 Жыл бұрын
I love python even more bcoz of you. You are absolutely amazing thanks & keep uploading such clips
@vorpal22
@vorpal22 Жыл бұрын
He's not teaching you modern Python practices. You should not use filter and map in Python 3.
@revenevan11
@revenevan11 Жыл бұрын
I'm just learning python, thanks for showing me the filter function!
@75424ht
@75424ht 9 ай бұрын
Thanks man you're the best!
@soumilbinhani8803
@soumilbinhani8803 9 ай бұрын
hey you can make this is_prime() function a bit more efficient by keeping x in the range(2,sqrt(num)+1) and keep an exception if-else for the number 1 hope that helps
@newgamingchannel6805
@newgamingchannel6805 9 ай бұрын
Thank you. I love your channel
@Nikhil-Tomar
@Nikhil-Tomar 9 ай бұрын
You could also use primes = [x for x in nums if is_prime(x)]
@rubenvanderark4960
@rubenvanderark4960 4 ай бұрын
``` from math import floor, sqrt def is_prime(x): if x==1: return False for i in range(floor(sqrt(x)): if x%i == 0: return False return True ```
@Jakku_Azzo
@Jakku_Azzo Жыл бұрын
He said, “Able Prize here I come”😂🔥
@KillToGame
@KillToGame 10 ай бұрын
scientists: use powerful computers to find new primes me: types infinity intead of 1000
@mr.luciddream6634
@mr.luciddream6634 20 күн бұрын
You could make it faster by defining a set where primes are stored and with each number check if it's a multiple of a prime in the set instead of the range [2,x). If it's not a multiple of 2 it ain't a multiple of 4 or 6.
@TheSkepticSkwerl
@TheSkepticSkwerl Жыл бұрын
This also 100% explains why functions are amazing. Return is better than break.
@gingeral253
@gingeral253 8 ай бұрын
You can also remove checks by going up to the square root of the value because anything past that would a repeat of something already checked.
@thesuperrancher9684
@thesuperrancher9684 22 күн бұрын
This is a problem I was literally working on today. I saw a really similar solution on stack overflow
@zakzak24
@zakzak24 10 ай бұрын
wow filter function is a time saver, before I used to go for the slower solution : for num in nums: if is_prime(num): print(nums[num]) else: continue ty for the vid🎉
@SolathPrime
@SolathPrime Жыл бұрын
you can do the same function but better cause if you know that every prime number can be written in the form of 6n + 1 or 6n - 1 except the multiples of prime numbers: 2, 3, 5, 7, 11 where n is a natural number
@zay1649
@zay1649 Жыл бұрын
bro what is that vscode theme its so nice
@hezztia
@hezztia Жыл бұрын
It's "SynthWave '84" from Robb Owen. It has an option (called "neon dreams") that makes the letters glowy, but i don't use it because i don't like it.
@Matias-rx1wk
@Matias-rx1wk Жыл бұрын
@@hezztiafont?
@Alpheamus
@Alpheamus Жыл бұрын
What python extension do you use in vscode? It's more colorful than mine and I'm jealous!
@AndoroidP
@AndoroidP Жыл бұрын
Just use Sieve of Eratosthenes, get better time complexity of O(nloglogn)
@SegFaultMatt
@SegFaultMatt Жыл бұрын
That’s the way I’d do it. Much better than this method, sad your only upvote is me.
@NathanSMS26
@NathanSMS26 Жыл бұрын
The prime thing was just an example to show off the filter function
@jackomeme
@jackomeme Жыл бұрын
Combine that with memorization, you can reduce the big O
@eck1997rock
@eck1997rock Жыл бұрын
Thanks for teaching job applicants to not format their code properly and also use a less readable alternative of list comprehensions.
@archigan1
@archigan1 Жыл бұрын
beat me to it
@kaniran1
@kaniran1 Жыл бұрын
Was looking for the list comprehension answer :-D
@johnr3936
@johnr3936 Жыл бұрын
Actually terrible way to write python. Do you think its just bait? I would not merge that
@the_lava_wielder6996
@the_lava_wielder6996 Жыл бұрын
Bro you guys unironically code in python it doesn't matter anyways
@eck1997rock
@eck1997rock Жыл бұрын
What should we use sensei?
@CreateCG1
@CreateCG1 Жыл бұрын
I am mew to python and u are helping a lot! Thanks
@RazeVX
@RazeVX 9 ай бұрын
Love to see a beginner friendly version of this codeing practice because I know how it looks after generations of programmer optimized the shit out of it in countless different languages since primes are essential for cryptography 😅
@davidmachado132
@davidmachado132 10 ай бұрын
Wow, that one was very helpful
@thedeegan
@thedeegan Жыл бұрын
range is non inclusive, so it gives you a list of numbers between 1-999.
@ryanhasmanners9997
@ryanhasmanners9997 Жыл бұрын
Or just do print([x for x in range(1000) if x%2==0])
@FarhanAlam-jb5xy
@FarhanAlam-jb5xy 2 ай бұрын
That just returns even numbers
@ethannguyen2551
@ethannguyen2551 9 ай бұрын
You check if it's divisible by every number up to it, but you really only need to check the previous prime numbers, since if it's divisible by a non-prime, it will also be divisible by its prime factorization.
@TarasZakharchenko
@TarasZakharchenko Жыл бұрын
Python dev meets functional programming for the first time :-D
@Xiaika
@Xiaika Жыл бұрын
You can massively improve performance of finding primes by searching between 2 and sqrt(n) since if we have two integers x and y such that n = x*y then it’s not possible for both x and y to be greater than the sqrt(n).
@natelance6713
@natelance6713 5 ай бұрын
If you're going to immediately turn it back into a list, don't use filter, use a list comprehension because it's faster. If you only need an iterator, then use filter.
@josgibbons6777
@josgibbons6777 9 ай бұрын
With the Sieve of Eratosthenes, you don't judge each number like that: you create a list of bools you update to eliminate multiples of whatever's still prime. It's more efficient.
@johannbauer2863
@johannbauer2863 Жыл бұрын
if you want to have a list of primes, use a sieve (e.g. sieve or erasthostenes or atkin) instead of this
@BlackLightning0Games
@BlackLightning0Games 7 ай бұрын
Make the range go to the sqrt(num) instead of num, because that is the max you can go without the smallest and largest of the multiples switching. To check is 49 is prime, you only have to check up to 7 because 7*7 = 49 This changes from o(n) to o(sqrt(n)) If you can do this it will save you on at least one coding interview.
@richardchurchill5181
@richardchurchill5181 Жыл бұрын
You do not need to check numbers from 2 to num. No divisor of greater than the square root of num needs to be checked if you check those less than that square root.
@fire17102
@fire17102 9 ай бұрын
Really nice, can you cover map? Also for prime check count up to the square root of num, not num :) ❤
@EternalCelestialChambers
@EternalCelestialChambers 12 күн бұрын
You can make the prime checking faster by first checking 2 and 3 then checking every (6 - 1) and (6 + 1) untill sqrt(n)
@tpd_
@tpd_ Жыл бұрын
Print(list(filter(list(map(lambda x: x is not any([x%y==0 for y un range (2,x)]), [i for i in range (1000)])))))
@RayTracingX
@RayTracingX 4 ай бұрын
Imao😮
@user-ns3js2ji4z
@user-ns3js2ji4z Жыл бұрын
The function is_prim can run til square of num to check if the number is prim😊
@ShillingTechy
@ShillingTechy 6 ай бұрын
Might save a few iterations if you check till x hits half of num instead if having num = 9 n you also check when x = 8
@Wyrmver
@Wyrmver Ай бұрын
there's a mathmatical formula that returns 1 if n is a prime
@lordfirespeed
@lordfirespeed Жыл бұрын
Nice demo of filter(). In reality one should use the Eratosthenes' sieve to obtain large lists of primes in python
@Rugg-qk4pl
@Rugg-qk4pl Жыл бұрын
In double reality one should download a large list of primes
@GordieGii
@GordieGii Жыл бұрын
Is that because it takes less time, less ram, fewer lines of code, or is easier to understand?
@Rugg-qk4pl
@Rugg-qk4pl Жыл бұрын
@@GordieGii Sieve is going to be significantly faster, but more lines of code. Not sure on the memory usage. But as long as it's clear you are implementing the sieve, difficulty to understand shouldn't be an issue.
@GordieGii
@GordieGii Жыл бұрын
@@Rugg-qk4pl That makes sense. The original video said that one objective was to save memory. Since range is an itterable, it only produces the next number and returns it to filter so the list only ever contains the primes. To do Eratosthenes' sieve you need to have all the numbers in the list and then prune them. I suppose you would only need a bool or a bit for each number, but then you would need bit handling routines. Probably already libraries for that sort of thing.
@piwi2775
@piwi2775 Жыл бұрын
I wish I knew this before my interview
@sven179
@sven179 Жыл бұрын
I was about to comment 1 is not prime and you only need to check up to the square root of a number to check if it’s prime. I was happy to see others already said this.
@philfernandez835
@philfernandez835 Жыл бұрын
square root + 1 right?
@sven179
@sven179 Жыл бұрын
@@philfernandez835 No, only up to the square root (and including it in the case that it happens to be an integer), but square root + 1 is completely unnecessary. The argument is as follows: suppose a number has no prime divisors
@zackm2299
@zackm2299 Жыл бұрын
I had to code that in assembly once
@Jakku_Azzo
@Jakku_Azzo Жыл бұрын
Had to code it in brain fuck the other day *cracks knuckles* R/iamverysmart
@llollercoaster
@llollercoaster Жыл бұрын
Beautiful exponential time complexity
@7268896
@7268896 Жыл бұрын
It's quadratic, not exponential
@llollercoaster
@llollercoaster Жыл бұрын
@@7268896 good catch. you're right
@oreoforlife720
@oreoforlife720 2 ай бұрын
Alternative way that is much easier to remember: condition list comprehension
@BlastGrip
@BlastGrip Жыл бұрын
You only need to test up to the square root of any given number when checking for primes.
@vorpal22
@vorpal22 Жыл бұрын
How did this not get upvotes? I said the same thing. This is way too much work being done.
@IThinkItsMe
@IThinkItsMe Ай бұрын
Thanks for this. Can I cast it to a set or tuple and get the same output? :-)
@loganselner521
@loganselner521 Жыл бұрын
The Pucci table
@mistermiggens5555
@mistermiggens5555 6 ай бұрын
Def getPrimes(array): ReturnVal = [] For I in range(len(array)): If math.sqrt(array[i]) == int(math.sqrt(array[i])): ReturnVal.append(array[i]) Return ReturnVal
@PriestPoppy
@PriestPoppy Жыл бұрын
You can also do: primes = [x for x in nums if is_prime(x) == True] And this will output a list of prime numbers without needing to convert it (if you instantly need to use the list and not the object)
@gavinhofer4588
@gavinhofer4588 Жыл бұрын
You don’t need the == True
@PriestPoppy
@PriestPoppy Жыл бұрын
@@gavinhofer4588 you're right! my bad
@OctagonalSquare
@OctagonalSquare 7 ай бұрын
If you ever have to find if a number is prime, you don’t have to divide by every number up until that number. You just have to divide by every number until half of that number. Cuts the amount of calculations by half
@raba9808
@raba9808 8 ай бұрын
There are so many ways to find prime, I'm surprised that finding prime numbers isn't already a built in function
@technowey
@technowey Жыл бұрын
This is a good tutorial for how to use a filter. However, there is an error in the program. 1 is *not* a prime number. There are also more efficient ways to filter prime numbers.
@1Richmar
@1Richmar 10 ай бұрын
pretty cool. You could also do list comprehensions which is native to the language. I believe it's the fastest native way to do this. Not sure though, as I'm a beginner in python lol
@Rushabh3d
@Rushabh3d Жыл бұрын
Wonderful bro !!!
@wz8881
@wz8881 Жыл бұрын
What VS Code color theme is this? I love it!
@BobChess
@BobChess 7 ай бұрын
Why does I get an energy drink after running this code 💀
@user-dk2tz1ww9x
@user-dk2tz1ww9x 4 ай бұрын
Well if all you wanted was to print you could iterate through the filter generator, and print each number, so no need to fill memory with list. In most cases you don't need to convert generator to concrete collection.
@Cristobal512
@Cristobal512 Жыл бұрын
This is so much easier to do in R.
@ai_panorama
@ai_panorama 10 ай бұрын
Thanks for sharing.
@leroyjenkins1911
@leroyjenkins1911 Жыл бұрын
When you eliminate every number which is dividable by num from the list you can improve your time complexity drastically.
@fri_punt_so
@fri_punt_so 9 ай бұрын
How do you record this? Audio while typing are seperate from the screen
@giovannip.6473
@giovannip.6473 Жыл бұрын
Little tip from me: The for loop doesn't need to loop over n, but is enough in range(2, n//2 + 1) 😉
@biank23
@biank23 Жыл бұрын
In fact, the loop is only necessary up to the square root of n
@alexwhitewood6480
@alexwhitewood6480 Жыл бұрын
@@biank23 this!
@darrenxavierjohan861
@darrenxavierjohan861 3 ай бұрын
1 is definitely my favorite prime number, innit?
@calvindibartolo2686
@calvindibartolo2686 Жыл бұрын
is your prime number filter dividing a number by every number between 2 and the number? Can you modulo it by the primes less than the sqrt of tested number as it's built? then you're only dividing it by the primes because if a number cannot be divided by a prime, then it must be prime. I'd imagine this would be significantly faster
@PabloEscobarmitzvah
@PabloEscobarmitzvah 7 ай бұрын
Good to check the potential factors twice to ensure we can display a nice "Loading..." screen 😊but in case you're looking for efficiency you could start by checking up to sqrt(n), because I'm pretty sure a*b = b*a for integers so if one of the factors is > sqrt(N), the other will for sure have to be below sqrt(N) and we can stop the primality check. I think you'd better show the use of a library rather than careless "tricks"
@mathadventuress
@mathadventuress 4 ай бұрын
Hey this is awesome thanks
@Broadsmile1987
@Broadsmile1987 10 ай бұрын
I thought you will do some clever caching of values to optimize the algorithm, and it's just a filter 💀 also you could unpack inside of print, no need to convert to list.
@AWriterWandering
@AWriterWandering Жыл бұрын
btw, your is_prime function has one oversight: 1 is not prime.
@genalkali1779
@genalkali1779 Жыл бұрын
if you want primes in a certain range it is faster to use the Sieve of Eratosthenes (look it up) it is actually really easy
@Saverax._33
@Saverax._33 Жыл бұрын
You can use MATCH and on the CASE put the IF statement
@midclock
@midclock 5 ай бұрын
I would focus on writing a condition that returns true as soon as possible, instead of having the truthy condition at the end of the function. The condition in the video is "pessimistic", as it defines something, by saying "something is not x". This example is simple, but there are complex scenarios where you want to have an exception at the bottom of your function, thrown when you're not able to determine an outcome. Cheers!
@utkarshsharma7459
@utkarshsharma7459 11 ай бұрын
Informative🎉
@Yupppi
@Yupppi 6 ай бұрын
This is really nice, but you can't save shorts to your playlists so you'd have a library of useful tips and methods.
@Lurkartiist
@Lurkartiist Жыл бұрын
I want to learn to code but it’s intimidating tbh . I’m no genius . Not gonna let that stop me from going for it though 💯
@AbdulRehman-rf2cc
@AbdulRehman-rf2cc 11 ай бұрын
less gooo
@bonquaviusdingle5720
@bonquaviusdingle5720 8 ай бұрын
it has a steep learning curve in the beginning but gets very easy, like learning to drive a car
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