Multiple 'or' condition in Python [duplicate]

Question

I have a little code issue and it works with IDLE and not with Eclipse, can I write this :

if  fields[9] != ('A' or 'D' or 'E' or 'N' or 'R'): 

instead of this :

if  fields[9] != 'A' and fields[9] != 'D' and fields[9] != 'E' and fields[9] != 'N' and fields[9] != 'R': 

Thank you.

Answer 1

Use not in and a sequence:

if fields[9] not in ('A', 'D', 'E', 'N', 'R'): 

which tests against a tuple, which Python will conveniently and efficiently store as one constant. You could also use a set literal:

if fields[9] not in {'A', 'D', 'E', 'N', 'R'}: 

but only more recent versions of Python (Python 3.2 and newer) will recognise this as an immutable constant. This is the fastest option for newer code.

Because this is one character, you could even use a string:

if fields[9] not in 'ADENR': 

Answer 2

You want the in operator:

if fields[9] not in 'ADENR':     ... 

Or, you could use any:

if not any(fields[9] == c for c in 'ADENR'):     ... 

Or, alternatively, all, which may have a bit more of the same form as the original:

if all(fields[9] != c for c in 'ADENR'):     ... 

---

As an aside:

if x != ('A' or 'B' or 'C'): 

is really the same thing as saying:

if x != 'A': 

because 'A' or 'B' or 'C' evaluates to 'A' (Try it!). The reason is because with or, python will return the first "non-falsey" value (or the last one if they're all falsey). Since non-empty strings are non-falsey, the first one gets returned.