I wrote this program that will tell you the two multiples factors of your input. Ex. if I were to input 35 (a semiprime), the program would print 5 and 7, which are the two prime numbers that multiply to 35.
But I am wondering if there is a more concise or pythonic way to iterate through this tuple so I wouldn't have to code all those "elif" statements you see below.
Also it would be great if I didn't need to rely on any external libraries.
# multiples of semiprimes 4 - 49
tuple1 = ( 2, 3, 5, 7 )
# tuple 1 calculations
while True:
try:
semiprime = int(input('Enter Semiprime: '))
except ValueError:
print('INPUT MUST BE AN INTEGER')
continue
# index 0 - 3
if (tuple1[0]) * (tuple1[0]) == semiprime:
print((tuple1[0]), (tuple1[0]))
elif (tuple1[0]) * (tuple1[1]) == semiprime:
print((tuple1[0]), (tuple1[1]))
elif (tuple1[0]) * (tuple1[2]) == semiprime:
print((tuple1[0]), (tuple1[2]))
elif (tuple1[0]) * (tuple1[3]) == semiprime:
print((tuple1[0]), (tuple1[3]))
# index 1 - 3
elif (tuple1[1]) * (tuple1[0]) == semiprime:
print((tuple1[1]), (tuple1[0]))
elif (tuple1[1]) * (tuple1[1]) == semiprime:
print((tuple1[1]), (tuple1[1]))
elif (tuple1[1]) * (tuple1[2]) == semiprime:
print((tuple1[1]), (tuple1[2]))
elif (tuple1[1]) * (tuple1[3]) == semiprime:
print((tuple1[1]), (tuple1[3]))
# index 2 - 3
elif (tuple1[2]) * (tuple1[0]) == semiprime:
print((tuple1[2]), (tuple1[0]))
elif (tuple1[2]) * (tuple1[1]) == semiprime:
print((tuple1[2]), (tuple1[1]))
elif (tuple1[2]) * (tuple1[2]) == semiprime:
print((tuple1[2]), (tuple1[2]))
elif (tuple1[2]) * (tuple1[3]) == semiprime:
print((tuple1[2]), (tuple1[3]))
#index 3 - 3
elif (tuple1[3]) * (tuple1[0]) == semiprime:
print((tuple1[3]), (tuple1[0]))
elif (tuple1[3]) * (tuple1[1]) == semiprime:
print((tuple1[3]), (tuple1[1]))
elif (tuple1[3]) * (tuple1[2]) == semiprime:
print((tuple1[3]), (tuple1[2]))
I hinted at this in my comment, but realized just the link to the function docs may not be enough.
Here's how you could write your code using itertools.combinations_with_replacement
:
from itertools import combinations_with_replacement
# multiples of semiprimes 4 - 49
tuple1 = ( 2, 3, 5, 7 )
# tuple 1 calculations
while True:
try:
semiprime = int(input('Enter Semiprime: '))
except ValueError:
print('INPUT MUST BE AN INTEGER')
continue
for (x,y) in combinations_with_replacement(tuple1, 2):
if x * y == semiprime:
print(x,y)
Much nicer, IMO :)
Edit : A previous version used itertools.combinations
which wouldn't yield (x,y) pairs with the same value (eg (x,y) = (2,2)
would never happen). combinations_with_replacement
allows for duplicates. Thanks to @Copperfield for pointing this out.
While jedwards demonstrates the most Pythonic approach - using the itertools
library which you will come to know and love- here is the more "classic" approach using for-loops for the pattern you want. I bring it up because as a programming beginner, it is important to know this basic, imperative idiom:
>>> tuple1 = (2,3,5,7)
>>> for i in range(len(tuple1)):
... for j in range(i+1, len(tuple1)):
... print(tuple1[i], tuple1[j])
...
2 3
2 5
2 7
3 5
3 7
5 7
>>>
Thus, your code would be shortened to:
for i in range(len(tuple1)):
for j in range(i+1, len(tuple1)):
if tuple1[i] * tuple1[j] == semiprime
print(tuple1[i], tuple1[j])
Even though @ jedwards solution is great, ( as well as concise/pythonic ); one other possible solution:
def prime_multiples(l,t ):
for i in l: # Iterate over our list.
for j in t: # Iterate over the tuple of prime factors.
# We check to see that we can divide without a remainder with our factor,
# then check to see if that factor exists in our tuple.
if i%j == 0 and i/j in t:
print "Prime factors: {} * {} = {}".format(j, i/j, i)
break # We could go not break to print out more options.
Sample output:
l = [4, 6, 9, 10, 14, 15, 21, 22, 25, 26, 33, 34, 35, 38, 39, 46, 49]
t = ( 2, 3, 5, 7 )
prime_multiples(l, t)
>>> Prime factors: 2 * 2 = 4
... Prime factors: 2 * 3 = 6
... Prime factors: 3 * 3 = 9
... Prime factors: 2 * 5 = 10
... Prime factors: 2 * 7 = 14
... Prime factors: 3 * 5 = 15
... Prime factors: 3 * 7 = 21
... Prime factors: 5 * 5 = 25
... Prime factors: 5 * 7 = 35
... Prime factors: 7 * 7 = 49
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