What does adding '=' do to bit operators in Python? (ie '

Question

What do the `<<=`and the `|=` operators mean Python? I guess they are bitwise operators. I know the operators `|` (bitwise or) and `<<` (bit shifting), but I don't know them in combination with the `=`. I found it in this piece code. Code below belongs to that code. ``` commandout = adcnum commandout |= 0x18 # start bit + single-ended bit commandout <<= 3 # we only need to send 5 bits here for i in range(5): if (commandout & 0x80): GPIO.output(mosipin, True) else: GPIO.output(mosipin, False) commandout <<= 1 GPIO.output(clockpin, True) GPIO.output(clockpin, False) ```

Accepted Answer

Both are in-place assignments; they effectively give you `name = name op right-hand-expression` in the space of just `name op= right-hand-expression`.

So for your example, you could read that as:

```
commandout = commandout | 0x18
commandout = commandout << 3
```

That is oversimplifying it a little, because with dedicated hooks for these operations the left-hand-side object can choose to do something special; `list += rhs` is really `list.extend(rhs)` for example, not `list = list + rhs`. An in-place operator gives a mutable object the chance to apply the change to `self` instead of creating a new object.

For your example, however, where I presume `commandout` is an int, you have immutable values and the in-place operation has to return a new value.

What does adding '=' do to bit operators in Python? (ie '<<=' instead of '<<')

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