I have the following problem from school: the teacher has asked us to divide to sides with 2/3 and 1/3 probabilities using the randint function.
I really don't understand how this randint function on probabilities works.
import random
rand = (random.randint(1,100))
if rand >= 67 :
print ("obj A 1/3")
else:
print ("obj B 2/3")
This does not work.
One key skill you must learn is using documentation. A quick search brought me to the Python manual page on random.randint():
Return a random integer N such that a <= N <= b.
Your creating a variable rand which is equal to a random number >= 1 and <= 100. The next line is a conditional that checks if your number is >= 67...this will only be true ~1/3 of the time.
Side note: there's no benefit to using a random number between 1-100. Your code would be much more straightforward (and therefore Pythonic) if you looked for exactly what you wanted (i.e. 1/3).
import random
rand = random.randint(1, 3)
if rand is 1:
print '1/3'
else:
print '2/3'
Why so complicated? Simplify to the level of your denominator: 3. Generate one of three integers, with equal probability. You'll get 1, 2, and 3; each appears 1/3 of the time.
rand = random.randint(1,3)
if rand == 1:
print ("obj A 1/3")
else:
print ("obj B 2/3")
Is this simple enough for you to understand? In your original code, you were generating 100 different integers. You did the "A" part in 34 of those cases. That's 34%, a little more than the requested 1/3.
random.randint(1,100)
This returns a number from 1 to 100. So, 1/3 is about 33 and 2/3 is about 66. So the first if statement is seeing that if the number is equal or greater than than 67, print "obj A 1/3", which is this part:
if rand >= 67:
print ("obj A 1/3")
Anything else, then print "obj A 2/3", which is the last part:
else:
print ("obj B 2/3")
Of course, you need to use print() like that and not like this, print () unless you want a Syntax error. Also, the math is wrong. The program should look more like this:
import random
rand = (random.randint(1, 3))
if rand == 1:
print("obj C 3/3")
elif rand == 2:
print("obj A 2/3")
elif rand == 1:
print("obj B 1/3")
The above math is the most accurate as you have a 1/3 chance of getting one of the numbers, which corresponds to the numerator in the fraction, x over 3, where rand is equal to x.
I think I see what you're trying to do but you need to start here by reading up on random. Check out this question/answer, I think it will explain things better. Your current code will get a syntax error, I think what you're looking to do is this:
import random
rand = (random.randint(1,100))
if rand >= 67:
print("1/3rd") # Do the 1/3rd things...
else:
print("2/3rd") # Do the 2/rd things...
I implore you to go read up on python though. PS. A more accurate solution would be to generate a random int from 1 to 3 instead of thinking of the problem in terms of 1-100. Then your probability becomes more accurate since 1/3rd = 33.3333... of the time, its hard to represent it using 1-100.
Related
On line 7 and 14 I cant figure out how to divide the variable.
import keyboard
import random
def main(Number, Start):
Number = random.randrange(1,100)
Start = False
QA = input('Press "K" key to begin')
if keyboard.is_pressed('K'):
Start = True
input('I"m thinking of a random number and I want that number divisible by two')
print(Number)
input('Please divide this by two. *IF IT IS NOT POSSIBLE RESTART GAME*\n')
if QA == int(Number) / 2:
print('.')
else:
print('.')
main(Number=' ' ,Start=' ')
What you probably want:
Pick a random number
Make user divide this number by two (?)
Do something based on whether the guess is correct
What is wrong with your code:
You are not picking a number divisible by two. The easiest way to ensure that your number is, indeed, divisible by two, is by picking a random number and then multiplying it by two: my_number = 2 * random.randrange(1, 50). Note the change in the range. Also note that the upper limit is not inclusive, which may be not what your meant here. A typical check for divisibility by N is using a modulo operator: my_number % N == 0. If you want users to actually handle odd numbers differently, you would need to write a separate branch for that.
input returns a string. In your case, QA = input('Press "K" key to begin') returns "K" IF user has actually done that or random gibberish otherwise. Then you are checking a completely unrelated state by calling keyboard.is_pressed: what you are meant to do here is to check whether the user has entered K (if QA == "K") or, if you just want to continue as soon as K is pressed, use keyboard.wait('k'). I would recommend sticking to input for now though. Note that lowercase/uppercase letters are not interchangeable in all cases and you probably do not want users to be forced into pressing Shift+k (as far as I can tell, not the case with the keyboard package).
input('I"m thinking of does not return anything. You probably want print there, possibly with f-strings to print that prompt along with your random number.
input('Please divide this by two. does not return anything, either. And you definitely want to store that somewhere or at least immediately evaluate against your expected result.
There is no logic to handle the results any differently.
Your function does not really need any arguments as it is written. Start is not doing anything, either.
Variable naming goes against most of the conventions I've seen. It is not a big problem now, but it will become one should you need help with longer and more complex code.
Amended version:
import random
import keyboard
def my_guessing_game():
my_number = random.randrange(1, 50) * 2
# game_started = False
print('Press "K" to begin')
keyboard.wait('k')
# game_started = True
print(f"I'm thinking of a number and I want you to divide that number by two. My number is {my_number}")
user_guess = input('Please divide it by two: ')
if int(user_guess) == my_number / 2:
# handle a correct guess here
print('Correct!')
pass
else:
# handle an incorrect guess here
pass
Alternatively, you can use the modulo operator % to test whether Number is divisible by 2:
if Number % 2 == 0:
print('.')
else:
print('.')
This will check whether the remainder of Number divided by 2 is equal to 0, which indicates that Number is divisible by 2.
The output shows a different result. Yes, the factorials of those numbers are right but the numbers outputted aren't right.
Here's the code:
input:
n = int(input("Enter a number: "))
s = 0
fact = 1
a = 1
for i in range(len(str(n))):
r = n % 10
s += r
n //= 10
while a <= s:
fact *= a
a += 1
print('The factorial of', s, 'is', fact)
Output:
Enter a number: 123
The factorial of 3 is 6
The factorial of 5 is 120
The factorial of 6 is 720
You're confusing yourself by doing it all in one logic block. The logic for finding a factorial is easy, as is the logic for parsing through strings character by character. However, it is easy to get lost in trying to keep the program "simple," as you have.
Programming is taking your problem, designing a solution, breaking that solution down into as many simple, repeatable individual logic steps as possible, and then telling the computer how to do every simple step you need, and what order they need to be done in to accomplish your goal.
Your program has 3 functions.
The first is taking in input data.
input("Give number. Now.")
The second is finding individual numbers in that input.
for character in input("Give number. Now."):
try:
int(character)
except:
pass
The third is calculating factorials for the number from step 2. I won't give an example of this.
Here is a working program, that is, in my opinion, much more readable and easier to look at than yours and others here. Edit: it also prevents a non numerical character from halting execution, as well as using only basic Python logic.
def factorialize(int_in):
int_out = int_in
int_multiplier = int_in - 1
while int_multiplier >= 1:
int_out = int_out * int_multiplier
int_multiplier -= 1
return int_out
def factorialize_multinumber_string(str_in):
for value in str_in:
print(value)
try:
print("The factorial of {} is {}".format(value, factorialize(int(value))))
except:
pass
factorialize_multinumber_string(input("Please enter a series of single digits."))
You can use map function to get every single digit from number:
n = int(input("Enter a number: "))
digits = map(int, str(n))
for i in digits:
fact = 1
a = 1
while a <= i:
fact *= a
a += 1
print('The factorial of', i, 'is', fact)
Ok, apart from the fact that you print the wrong variable, there's a bigger error. You are assuming that your digits are ever increasing, like in 123. Try your code with 321... (this is true of Karol's answer as well). And you need to handle digit zero, too
What you need is to restart the calculation of the factorial from scratch for every digit. For example:
n = '2063'
for ch in reversed(n):
x = int(ch)
if x == 0:
print(f'fact of {x} is 1')
else:
fact = 1
for k in range(2,x+1):
fact *= k
print(f'fact of {x} is {fact}')
So, I wrote a code to find if a number is PRIME or NOT...
I wrote it in 2 different ways, they are almost same but I just had a doubt. So here it is:
1st code:
num = int(input("Enter the number: "))
lim = num//2 + 1
for i in range(2,lim):
if num % i == 0:
print("Prime!")
break
else:
print("Not Prime!")
2nd Code:
num = int(input("Enter the number: "))
for i in range(2,num):
if num % i == 0:
print("Prime!")
break
else:
print("Not Prime!")
The 1st code takes the input(num) and according to the input sets a limit(which is the half number + 1)
and then checks if the num is divisible by all the numbers in range (2 to lim)
The second one is same but instead of setting a limit it just checks all numbers lower than the input, which means it has to do a little more work...
Now both of these are almost same, the only difference is I saved a line in 2nd one and output efficiency is also better!
Which code would you want me to prefer/
also if this code has any problems, pointing them out would be helpful!
Thanks :)
Explanation
The most important piece of iteration, namely determining whether a number is prime or not, is to keep track of it. Without this process and in the OP's program, a variable is not used to handle this, meaning that he checks whether a number is or isn't prime every single time and concludes at that point. He also uses an else statement which is syntactically incorrect.
To prevent this, we can use a variable to keep track of this. Let's call it isprime. We need to assume that a number will always be a prime unless otherwise said. This can be achieved by setting isprime to default be True, and setting it to be False when we conclude that it is not a prime, because is has a divisor. Finally, we can check this variable at the end and determine whether that number is a prime or not, because it would be set to False if not, or left as True if it is.
Another observation made is that the limit for determining primes can be reduced down to sqrt(n). This is because we do not need to find every factor if it exists, just its lowest corresponding factor. Let's look at an example:
Factors of 24: 2, 3, 4, 6, 8, 12
We can stop checking for the factors right here:
2, 3, 4 | 6, 8, 12, 24
This is because if a number has a factor (such as greater than the square root), it will have a corresponding factor less than the square root. As a result, we can set our limit to be sqrt(n), just for peace of mind + a time complexity of O(sqrt(n)) v. O(n).
As an extra note, sqrt is not inbuilt into Python. You will have to import it from the math library using:
from math import sqrt
Final Code
# Setup
num = int(input("Enter the number: "))
lim = sqrt(num)
isprime = True
# Loop & check
for i in range(2,lim):
if num % i == 0:
isprime = False
break
# Results
if isprime:
print("Prime!")
else:
print("Not prime!")
The logic of the solution is wrong. You gave to switch the "Prime" and "Not Prime" tags. Like follows;
num = int(input("Enter the number: "))
lim = num//2 + 1
for i in range(2,lim):
if num % i == 0:
print("Not Prime!")
break
else:
print("Prime!")
The solution 1 is more efficient because you do not need to do extra
computation to check num//2 + 1. So it is preferable.
Sorry if my post is messy or hard to understand. I am just learning to code and to understand python. I have a homework where I am given n1 (random number from 0-10) and n2(from 30-45). My job is to print every number between n1 and n2 that is divisible by 2 but not by 3.
for x in range(n1,n2):
if x%2==0:
print(x)
if x%3==0:
continue
So this is my code now. I have tried it and it works, but it prints numbers like 6 and 12 that are divisible by 3. Hod do I fix it?
You just need to add an extra condition here:
for x in range(n1,n2):
if x % 2 == 0 and x % 3 != 0:
print(x)
Or to have the continue happen before the print such as:
for x in range(n1,n2):
if x%3 == 0:
continue
if x%2 == 0:
print(x)
What was happening was that you were printing first, and then checking the condition for divisibility by 3, which meant that even though you "skipped" the loop, you had already printed anyway.
You need to choose random number between 0-10 for n1 and 30-45 for n2. Import random module and use randint() to get random nos. Also, you can put both the conditions in same if statement. Your code:
import random
n1=random.randint(0,10)
n2=random.randint(30,45)
for i in range(n1,n2):
if i%2==0 and i%3!=0:
print(i)
Have a little problem. I'm writing a simple program that takes an input of numbers (for example, 1567) and it adds the odd numbers together as well as lists them in the output. Here is my code:
import math
def oddsum(n):
y=n%10
if(y==0):
return
if(y%2!=0):
oddsum(int(n/10))
print (str(y),end="")
print (" ",end="")
else:
oddsum(int(n/10))
def main():
n=int(input("Enter a value : "))
print("The odd numbers are ",end="")
oddsum(n)
s = 0
while n!=0:
y=n%10
if(y%2!=0):
s += y
n //= 10
print("The sum would be ",end=' ')
print("=",s)
return
main()
It outputs just fine, in the example it will print 1 5 and 7 as the odd numbers. However, when it calculates the sum, it just says "7" instead of 13 like it should be. I can't really understand the logic behind what I'm doing wrong. If anyone could help me out a bit I'd appreciate it :)
I understand it's an issue with the "s += y" as it's just adding the 7 basically, but I'm not sure how to grab the 3 numbers of the output and add them together.
As #Anthony mentions, your code forever stays at 156 since it is an even num.
I would suggest you directly use the string input and loop through each element.
n = input("Enter a value : ") #'1567'
sum_of_input = sum(int(i) for i in n if int(i)%2) #1+5+7=13
[print(i, end="") for i in n if int(i)%2] #prints '157'
Note that int(i)%2 will return 1 if it is odd.
1567 % 10 will return 7. You might want to add the numbers you printed in oddsum to a list, and use the sum function on that list to return the right answer.
The immediate issue is that n only changes if the remainder is odd. eg 1,567 will correctly grab 7 and then n=156. 156 is even, so s fails to increment and n fails to divide by 10, instead sitting forever at 156.
More broadly, why aren't you taking advantage of your function? You're already looping through to figure out if a number is odd. You could add a global parameter (or just keep passing it down) to increment it.
And on a even more efficient scale, you don't need recursion to do this. You could take advantage of python's abilities to do lists. Convert your number (1567) into a string ('1567') and then loop through the string characters:
total = 0
for c in '1567':
c_int = int(c)
if c_int%2!= 0:
total += c_int
print(c)
print(total)