Using the and operator to check if two values equal a third

[DBS]

Hello,

Newbie question here, which is the correct way to use the and operator if checking to see whether two values equal a third value:

if a == b and c == b:
   do something

if a and c == b:
   do something
   
if b in (a,c):
   do something

[Yoriz]

The first one would work.
The second would always be true regardless of value a if b and c where equal.
The third would be true if b was either a or c

[metulburr]

This suspiciously sounds like a test question.

[DBS]

Thanks. It's not a test question. I was not sure how to see if two values equal the same value. The second option makes the most sense to me, but I forget you have to compare each value to the third value as in the first option.

[Mekire]

I believe you can chain the == operator without an and with no issues:

if a == b == c:

[buran]

The second would always be true regardless of value a if b and c where equal.

Not if a is None, 0, empty list, empty tuple, empty dict, etc. i.e. everything that would evaluate to FALSE

a=None
b=1
c=1
print 'a={}, b={}, c={}'.format(a,b,c)
if a and b == c:
    print 'It is TRUE'
else:
    print 'It is FALSE'

Output:
a=None, b=1, c=1

It is FALSE

[nilamo]

I believe you can chain the == operator without an and with no issues:

if a == b == c:

Really?  Hmm....

>>> a = 0
>>> b = 0
>>> c = 0
>>> a == b == c
True

I'm not sure that should be used in practice, as when I saw that I immediately thought it'd fail, since in my mind (a==b) becomes a bool, and c!=True.

[ichabod801]

I'm not sure that should be used in practice, as when I saw that I immediately thought it'd fail, since in my mind (a==b) becomes a bool, and c!=True.

Ah, but then this wouldn't work either:

if -10 < x < -2:

Also note:

>>> a, b, c = 0, 0, 0
>>> (a == b) == c
False

[sparkz_alot]

I'm not sure that should be used in practice, as when I saw that I immediately thought it'd fail, since in my mind (a==b) becomes a bool, and c!=True.

Ah, but then this wouldn't work either:

if -10 < x < -2:

Also note:

>>> a, b, c = 0, 0, 0
>>> (a == b) == c
False

Doesn't the order of precedence still apply and the parenthesis just become redundant? I mean obviously they don't, but why? Never mind... took me a moment to wrap my head around what was happening

[nilamo]

Never mind... took me a moment to wrap my head around what was happening

Exactly why I don't think that should be used :p