Is there anyone who thinks this is a bad idea for checking for odd numbers, and adding them to a list for later use?
nums_list = []
for number in range(1000): # This makes a list with a ton of uneven numbers.
eoro_check = (number-1)%2
if eoro_check == 0:
pass
else:
if number-1 == -1:
pass
else:
nums_list.append(number-1)
print nums_list
nums_list=[n for n in range(1000) if n%2]
In plain English, nums_list is each item in range(1000) IF that item is not evenly divisible by 2.
This works because if n is even, then n%2 is 0 (evenly divisible by 2) and therefore False. If n is odd, n%2 is 1, and therefore true.
@Webmaster4o
Yeah, I understand what it does. But is there another built-in/more efficient way of doing it?
@AtomBombed Actually, I might have something else. range(1,1000,2) is more efficient both time wise, and length wise, and it's pretty "built in". That's as "built-in" as you're gonna get.
However, if you're not looking for odd numbers and that's just an example, then a list comprehension is a pretty good method for general checking, the most compact and most efficient that I know of.
@Webmaster4o alright, thanks!
In Python 2, you should almost always choose to use xrange() instead of range() for performance and memory management reasons...
import sys
print(sys.getsizeof(range(1000))) # 8064
print(sys.getsizeof(xrange(1000))) # 20
print(sys.getsizeof(range(1000000))) # 4000032 that is 4MB of RAM instead of 20 bytes
print(sys.getsizeof(xrange(1000000))) # 20
@ccc oh thanks! I had no idea the difference. I didn't even know there was an xrange(). I will be sure to use that, as I use for loops with range() a ton.
The thing that will really warp your mind is that the range() implementation is removed from Python3 and the xrange() implementation is improved to deal with arbitrarily large numbers and renamed to range().
http://stackoverflow.com/questions/15014310/why-is-there-no-xrange-function-in-python3
@ccc that's interesting. Too bad I wouldn't know as omz refuses to work on getting Python 3 in.
That is why God invented other computers.
@ccc lol, I am getting one.
@AtomBombed
omz refuses to work on getting Python 3 in.
I think that's a little harsh, he's just finished the fantastic 2.0 update, and he hasn't said he won't upgrade, it's just not his top priority.