What does do in python?

Question

I just saw an expression like 1 and "b" in python code and even 1 and "a" or "b".

I checked the help for int and figured out that and means bitwise and with two integers

__and__(...)
 |      x.__and__(y) <==> x&y

but there's no mention of a str as second operand. I assume that there's no way that the str can be interpreted as int because there's just no way of conversion or casting and that I'm thus missing a meaning of and.

Then I started experimenting to get the first expression above to be 1, but no success.

No, `&` is bitwise - `x and y` is really `x if bool(x) else y`. — jonrsharpe, Sep 09 '15 at 14:21
This is just boolean logic. `and` returns the first argument if that is true, otherwise the second argument. — Daniel Roseman, Sep 09 '15 at 14:21
@DanielRoseman how come `'foo' and 1` returns `1` even though `'foo'` evaluates `True`? — Lawrence Benson, Sep 09 '15 at 14:23
Argh, wrong way round. it returns the first argument if that is *false*, otherwise the second. — Daniel Roseman, Sep 09 '15 at 14:24

Martijn Pieters · Answer 1 · 2015-09-09T14:28:20.420

1

__and__ is used for the bitwise operator &. and is a logical, boolean operator, and is not handled by a special method, because it short-circuits (if the first expression evaluates to false, the second expression is not even executed).

You simply have a boolean expression, and the standard truth value testing rules apply here.

edited Sep 09 '15 at 14:28

answered Sep 09 '15 at 14:22

Martijn Pieters

1,048,767
296
4,058
3,343

What does do in python?

1 Answers1