What are the meanings of the "~" and "&=" symbols in python?

Question

I saw the following in a python group:

>> bookStyle = aui.AUI_NB_DEFAULT_STYLE
>> bookStyle &= ~(aui.AUI_NB_CLOSE_ON_ACTIVE_TAB)

Could you explain the second statement?? What does &= and ~ do?

Answer 1

As per the bitwise operators documentation,

The unary ~ (invert) operator yields the bitwise inversion of its plain or long integer argument. The bitwise inversion of x is defined as -(x+1). It only applies to integral numbers.

&= can be understood like this

bookStyle = bookStyle & ~(aui.AUI_NB_CLOSE_ON_ACTIVE_TAB)

So, we basically, invert the value of aui.AUI_NB_CLOSE_ON_ACTIVE_TAB and then check if all the ON bits in the inverted value are ON in bookStyle as well.

The ~ can be understood better with 32 bit arithmetic like this

5 can be represented in 32 bit Binary like this

print format(5 & (1 << 32) - 1, "032b")
# 00000000000000000000000000000101

Now, when we do ~5 result will be

print ~5
# -6

So, lets print -6 in Binary

print format(-6 & (1 << 32) - 1, "032b")
# 11111111111111111111111111111010

If we compare the values,

00000000000000000000000000000101
11111111111111111111111111111010

you get the idea what exactly is happening internally.