# Always returns none?

#1

My function always returns None instead of False or True

I’m not sure why I keep getting none because I have the return statements… are they indented/placed incorrectly?

``````

def is_prime(x):
if x < 1:
return False
else:
for n in range(2, x - 1):
if x % n == 0:
return False
else:
return True

``````

#2

update

messed with the code and found a few things I’ve left out. Now my function seems to be failing on is_prime(9), though I can’t pinpoint why.

``````def is_prime(x):
if x <= 1:
return False
elif x == 2 or x == 3:
return True
else:
for n in range(2, x - 1):
if x % n == 0:
return False
else:
return True
``````

#3

Examine the following brute force approach I believe is implied in the exercise…

``````>>> def is_prime(x):
if x < 2: return False
for n in range(2, x):
if not (x % n): return False
return True

>>> is_prime(17)
True
>>> is_prime(0)
False
>>> is_prime(9)
False
>>>
``````

I hope at this point you understand the logical `not`.

``````x % n == 0    # True if no remainder

x % n         # True if is a remainder

not (x % n)   # True if no remainder``````

#4

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