Bitten by my C/Java experience

[Tobiah]

On 05/04/2015 08:20 AM, Cecil Westerhof wrote:
> Potential dangerous bug introduced by programming in Python as if it
> was C/Java. :-(
> I used:
>      ++tries
> that has to be:
>      tries += 1
>
> Are there other things I have to be careful on? That does not work as
> in C/Java, but is correct syntax.
>

One surprise for the new user is an otherwise handy rule of scope.
A variable in a function will by default access any global variables of
the same name *unless* it is assigned to in the function.

def glob():
         print "global:", foo

def loc():
         foo = 2
         print "local:", foo

def alt():
         global foo
         foo = 1
         print "altered:", foo

foo = 3

glob()
print "Original:", foo

loc()
print "Original:", foo

alt()
print "Original:", foo

################# Output ##################

global: 3
Original: 3
local: 2
Original: 3
altered: 1
Original: 1