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Teaching python (programming) to children

Duncan Booth duncan at NOSPAMrcp.co.uk
Fri Nov 9 05:03:09 EST 2001 
hungjunglu at yahoo.com (Hung Jung Lu) wrote in 
news:8ef9bea6.0111060838.24996280 at posting.google.com:

> How soon does a beginner run into the following problem? (see also the
> "How much is set in stone?" thread)
> 
> #------------------
> flag = 0
> 
> def f(x):
>     flag = 1
>     return 2*x
> 
> y = f(3)
> print y, flag
> #------------------
> output: 
> 6 0
> 
<snip>

> (2) After being shocked by the above example, students start to put
> 'global' statements in every single function for every single
> variable. They don't understand what is going on, they just don't want
> to be bitten by the same bug, again.

So perhaps the students should be taught not to use the global statement at 
all in situations like the one above:

   def f(x):
      return 2*x, 1
 
   y, flag = f(3)

And if they need to store state, it may be time to introduce classes:

class F:
   def foo(self, x):
      self.flag = 1
      return 2*x

f = F()
y = f.foo(3)

-- 
Duncan Booth                                             duncan at rcp.co.uk
int month(char *p){return(124864/((p[0]+p[1]-p[2]&0x1f)+1)%12)["\5\x8\3"
"\6\7\xb\1\x9\xa\2\0\4"];} // Who said my code was obscure?
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