Question

Possible Duplicate:
Python: Behaviour of increment and decrement operators

>>> a=2
>>> ++a
2
>>> a++
Traceback (  File "<interactive input>", line 1
    a++
      ^
SyntaxError: invalid syntax
>>> ++a
2

why ++x is OK?

(I’m asking since someone at work habitually wrote ++i, which didn’t do as (habitually) expected, but didn’t throw an error either, so it took some time to find the bug.)

Answer 1

It means +(+a), i.e. opposite to the meaning of -(-a) (although obviously in this case, the result is the same!)

See http://docs.python.org/library/stdtypes.html#numeric-types-int-float-long-complex.