CODEWITHSUNDEEP
pythonnestedwhile-loop
patch321
patch321

Reputation: 13

Why is my nested while loop not working

Working on a program in python to print out the first 1000 prime numbers (except 2). all i can get for the output is the number 3. don't understand where or when my loop is ending. very new at programming. can anybody help?

primeCounter = 1
candidate = 3

while primeCounter < 1000:
    isPrime = True
    counter = 2
    while counter < candidate:
        if candidate%counter == 0:
            isPrime = False
        else:
            counter = counter + 1

    if isPrime == True:
        print candidate
        primeCounter = primeCounter + 1

     candidate = candidate + 1

Upvotes: 1

Views: 2648

Answers (3)

Valentin Briukhanov
Valentin Briukhanov

Reputation: 1283

Your problem in block

while counter < candidate:
    if candidate%counter == 0:
        isPrime = False

if not candidate % counter, you get infinity loop.

Upvotes: 0

David Schwartz
David Schwartz

Reputation: 182875

Once you set isPrime to False, you never increment counter again, so you never get out of the inner while loop.

Upvotes: 2

qiao
qiao

Reputation: 18229

primeCounter = 1
candidate = 3

while primeCounter < 1000:
    isPrime = True
    counter = 2
    while counter < candidate:
        if candidate%counter == 0:
            isPrime = False
            break # <<<<<<<<<<<<<<<<<   break here, or the loop will go infinite
        else:
            counter = counter + 1

    if isPrime == True:
        print candidate
        primeCounter = primeCounter + 1

    candidate = candidate + 1

Upvotes: 3

Related Questions