Why can't I use the '|' bitwise operator in this statement?

But what is an example of where I can use it?

Aside from operations on bitfields, a bitwise operator can be useful in several "non bits" cases. For instance:

value & 1 evaluates to 1 if value is odd (and will evaluate to True in an if statement)
value >> 1 divides value by 2 (integer division)

But usually bitwise operators are for when you want to manipulate bits in values. For instance:

value | 5 returns value with bits 1 and 3 set to True
value & 0xffff returns the 16 least-significant bits in value (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 of value with bits 1 and 3 set to False

Etc.

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:

• 25: 0b00011001
• 10: 0b00001010
• 5: 0b00000101

(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):

• 0 | 1 = 1
• 1 | 0 = 1
• 0 | 0 = 0
• 1 | 1 = 1
• 1 | 0 = 1
• 0 | 0 = 0 for all the rest

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...

 py

    
    if coin == 25 | 10 | 5:  # if coin == 31
        ...
    if coin == 25 + 10 + 5:  # if coin == 40
        ...

  

...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.

    
0d10 = 0b00001010
0d04 = 0b00000100

1010   |
0100
------
1110

0b00001110 = 0d14


0d25 = 0b00011001
0d10 = 0b00001010

11001   |
01010
-------
11011

0b00011011 = 0d27

  

If an int is only x bytes long, but y bytes are needed for an action, it's just padded with 0's to the left. So 0b110 = 0b0110 = 0b00000110. Usually you will use either 8, 16, 32 or 64 digits/bits (char, short, int and long respectively, and 1, 2, 4 and 8 bytes long, 1 byte = 8 bits. So you'll usually align it with bytes.) However, for calculating like this removing trailing zeroes can make it more tidy, and sometimes 4 or 2 bits are used too. And bools technically only use 1 bit.