Why is the expression (0==0 & 1==1) evaluating to False?

Question

Similarly (-1==-1 & 1==1) is also False.

Apologies if this is something obvious but I can't find an explanation for it.

Answer 1

& is the bitwise AND operator. As mentioned in the documentation, Bitwise operators have higher precedence than logical operators, so

0 == 0 & 1 == 1

Becomes

0 == (0 & 1) == 1

And you can imagine it goes downhill from there:

   0 == (0 & 1) == 1
=> 0 == 0 == 1
=> 0 == 0 and 0 == 1
=> True and False 
=> False

Assuming what you wanted was a logical AND, the python way to do that would be using and:

0 == 0 and 1 == 1

Which gives you True as you'd expect.

Answer 2

Lets break this up.

The highest priority sign here is the brackets. Except we're wrapping the entire expression, so they don't do anything.

Next we have the bitwise operator &.

0 & 1 which equals 0.

This leaves us with 0 == 0 == 1

As 0 does not equal 1, we get False.

For reference, here is the python documentation about operator precedence.