Lesson 5: Listing up all prime numbers using for loop

posted Nov 2, 2017, 8:00 AM by Attila Lengyel   [ updated Nov 2, 2017, 10:47 AM ]
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Developed version in class
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total = 0
for x in range(2,100):
  prime = True
  for y in range(2,x):
    if x % y == 0:
      prime = False
  if prime == True:
    print (x, "is a prime number")
    total = total + 1
   
print("There are", total, "number of prime number")

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Optimized version post-class
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total = 0
iterations = 0
upper = 100000
primelist = []

for x in range(2,upper):
  prime = True
  for y in primelist:
    iterations += 1
    if x % y == 0:
      prime = False
      break
  if prime == True:
    total += 1
    primelist.append(x)
   
print("There are", total, "prime numbers till", upper)
print("I've have found them in ", iterations, "interatitons")
print("They are ", primelist)

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