if coin == 25 | 10 | 5:
If I replace the ‘|’ with ‘or’ the code runs just fine. I’m not sure why I can’t use ‘|’ in the same statement.
Doing the following doesn’t work either:
if if coin == 25 | coin == 10 | coin == 5:
I know bitwise operators can only be used with integers, but other then that is there another difference from logical operators?
Much to unpack here…
…will evaluate as True if coin is equal to the binary OR of 25, 10 and 5 - i.e. 31. In other word, it’s equivalent to
coin == 31. That’s because the bitwise OR has precedence over the == operator. See operator precedence in Python.It probably doesn’t. If you replace
|withor, you have the statementcoin == 25 or 10 or 5which is always True in theifstatement because it’s evaluated as(coin == 25) or (not 0) or (not 0)in anifstatement.…will evaluate as
coin == (25 | coin) == (10 | coin) == 5. Again, operator precedence.What you want to do is this:
if coin in [25, 10, 5]:or
if coin in (25, 10, 5):or simply
if coin == 25 or coin == 10 or coin == 5:Don’t create problems and confusion for the next guy who reads your code for nothing. Simple and readable are your friends 🙂
Thanks. I think I understand why I wouldn’t want to use it in this case. But what is an example of where I can use it? This makes me think I should avoid using bitwise operators with integers and keep it to strings only, but I know that’s not true from what I’ve learned.
When you’re working with the binary representation of numbers.
In your code you had three numbers 25, 10 and 5. If we write those number in binary we get:
(The 0b at the start is just a way of saying “this is binary”)
When you do a bitwise-or, it’s a bit like adding up but you don’t bother with carrying anything. So let’s do 25 | 10, starting at the right-hand end going bit by bit (bitwise):
So the result is 0b00011011 which is 27.
So now you’re asking “when would I ever need to do such a thing?” and the flippant answer is “you’ll know when you need it”.
You’re looking for more though, I know. Basically computers often put multiple bits of data into bitstreams (long sequences of bits). Think networking and file storage. Constructing these bitstreams is done with bitwise operators like |, &, ^, << and >>. Together they form a different type of maths to what you’re used to.
These operators work in a very similar way to how +, -, * and / work. They take two numbers and return a third. If we rewrite your code using operators you’re more familiar with…
…you can see it’s obviously wrong because you’re doing one comparison with the result of the operation (addition or bitwise-or), not three comparisons.
Aside from operations on bitfields, a bitwise operator can be useful in several “non bits” cases. For instance:
value & 1evaluates to 1 ifvalueis odd (and will evaluate to True in anifstatement)value >> 1dividesvalueby 2 (integer division)But usually bitwise operators is for when you want to manipulate bits in values. For instance:
value | 5returnsvaluewith bits 1 and 3 set to Truevalue & 0xffffreturns the 16 least-significant bits invalue(usually you do this to make sure it will fit in 2 bytes in memory for example)value & (0xffff ^ 5)returns the lower 16 bits ofvaluewith bits 1 and 3 set to FalseEtc.
Thank you for the reply. It seems bitwise operators are somewhat of an advanced concept that I may revisit down the road.
honestly yes you’re probably not going to use them a lot, if at all, especially in python
You might use them with sets:
a = {1, 2, 3} b = {2, 3, 4} a | b # {1, 2, 3, 4} a & b # {2, 3} a ^ b # {1, 4} a - b # {1} b - a # {4}They’re quite simple. Just convert the values to binary and apply the applicable truth tables. Just remember operator precedence when you use them, and in doubt, don’t trust your luck and apply parentheses generously 🙂