How do I understand "and" in a loop

[leoahum]

Hi,

I'm trying to get a better understanding for "and" in a loop. For the script below, I'm trying to get index 1, but it returns index 1 and 2.

b = ["abc", "bcd","cde"]

for i in range(len(b)):
    if "b" and "d" in b[i]:
        print (i)

if I change it like this, and expected no returns (cause none item in b has "bc" and "cd" at the same time), it actually gives me index 1 and 2 again.

b = ["abc", "bcd","cde"]

for i in range(len(b)):
    if "bc" and "cd" in b[i]:
        print (i)

Can someone help? Thanks!

[bowlofred]

"and" isn't special in a loop. You're probably getting confused by precedence. and has fairly low precedence, lower than in. So the expression in your first example should be parsed this way:

if ("b") and ("d" in b[i]):

"b" is always true, so the branch is taken whenever "d" is found in b[i], which is the indexes you describe. Your second example is similar.

if ("bc") and ("cd" in b[i]):

True whenever "cd" is in b[i], which is correct for index 1 and 2.

You probably want something similar to this:

if "b" in b[i] and "d" in b[i]:

or

if all(x in b[i] for x in "bd"):

[leoahum]

Thanks a lot!