Euler 3 code - doesn't work PYTHON

[tawfiqh]

i couldn't get my code for project euler problem 3 to work:

so i got this code for finding a prime in python:



num = input('Enter the number which you wish to determine it is prime: ')

if num < 2:
print "\nThe Number", num, " is not a prime!"
else:
for div in range(2, (num/2)+1):
if num%div==0:
print "\nThe Number", num, " is not a prime!"
break
else:
print "\nThe Number", num, " is a prime!"


I incorporated it into my program but it doesn't work


y=24
x=1
f=[]
pf=[]
while x<=y:
if y%x==0:
f.append(x)
if x < 2:
print "\nThe Number", x, " is not a prime!"
elif x>2:

for div in range(2, (x/2)+1):
if x%div==0:
break
else:
pf.append(x)


x=x+1

print f
print pf


it just ouputs:


The Number 1 is not a prime!
[1, 2, 3, 4, 6, 8, 12, 24]
[]

why doesn't it work?

[Arndt]

i couldn't get my code for project euler problem 3 to work:

so i got this code for finding a prime in python:



num = input('Enter the number which you wish to determine it is prime: ')

if num < 2:
print "\nThe Number", num, " is not a prime!"
else:
for div in range(2, (num/2)+1):
if num%div==0:
print "\nThe Number", num, " is not a prime!"
break
else:
print "\nThe Number", num, " is a prime!"


I incorporated it into my program but it doesn't work


y=24
x=1
f=[]
pf=[]
while x<=y:
if y%x==0:
f.append(x)
if x < 2:
print "\nThe Number", x, " is not a prime!"
elif x>2:

for div in range(2, (x/2)+1):
if x%div==0:
break
else:
pf.append(x)


x=x+1

print f
print pf


it just ouputs:


The Number 1 is not a prime!
[1, 2, 3, 4, 6, 8, 12, 24]
[]

why doesn't it work?

Because you have changed the indentation at one place when you included the first code into your program: the 'else' goes with the 'for', not with the 'if'. As you probably know, in python, indentation is significant for specifying the control structure.

[benj1]

if num%div==0:
print "\nThe Number", num, " is not a prime!"
break
get rid of the break it breaks out of the for loop

[Arndt]

if num%div==0:
print "\nThe Number", num, " is not a prime!"
break
get rid of the break it breaks out of the for loop

Admittedly, the OP didn't say what the correct result should be.

[tawfiqh]

i got it to work a different way. (similar)

using


def prime(num):
if num < 2:
f.append(x)
else:
for div in range(2, (num/2)+1):
if num%div==0:
print "\nThe Number", num, " is not a prime!"
break
else:
print "\nThe Number", num, " is a prime!"
y=600851475143
x=1
f=[]
pf=[]
while x<=y:
if y%x==0:
prime(x)
x=x+1

#print f
#print pf
print pf [-1]


it prints out a list of prime factors then starts printing a list of factors, the it lags to hell so i just take the last prime factor it lists
:p