[Tutor] finding factorials - hmm..., gcd

[glingl]

--- Payal Rathod <payal-python@staticky.com> schrieb:
..
> Commented example below. Print statements are now numbered.
> 
>  print "WHAT'S GOING ON?"
>  x =4
>  y=10
>  z = 0
>  print "x =",x,"y =",y,"z =",z	# -------> (1)
>  
>  def look(a,b):
>     print "x =",x,"y =",y,"z =",z,"a =",a,"b =",b # --------> (2)
>     a=2*a
>     b=2*b
>     c=a*b
>     print "x =",x,"y =",y,"z =",z,"a =",a,"b =",b,"c =",c # ------> (3)
>     return c
>     c = c*c       # ;-)
>     print "x =",x,"y =",y,"z =",z,"a =",a,"b =",b,"c =",c   # -----> (4)
>  
>  print "x =",x,"y =",y,"z =",z	# ------------> (5)
>  z = look(x,y)     # this will execute 2 (!) print-statements
>  # you won't be able to print a,b,c here
>  print "x =",x,"y =",y,"z =",z	# ---------> (6)
> 
> 
> The output is,
> 
> WHAT'S GOING ON?
> x = 4 y = 10 z = 0	# This comes from print statement (1)
right!
> x = 4 y = 10 z = 0      # This comes from print statement (5)
right!
> x = 4 y = 10 z = 0 a = 4 b = 10  
> # Where the world this comes from? 
from print statement (2), which gets executed whenever the function
look is called
> # a and b are never defined anywhere,
the are! in the first line of the definition of look:
def look(a,b)
a and b get created, every time you call look - an destroyed
every time the execution of look has ceased.
> # nor are they assigned values of x and y.
They are! When look(x,y) is called, a gets the value of x
and b gets the value of y. (Think of: a and b are substituted
by x and y). You can substitute other values, e.g. by calling
look(1001,-1)
> # Where did python get the
> # idea that a = 4 and b = 10?
When look(x,y) is called, a gets the value of x
and b gets the value of y. (Think of: a and b are substituted
by x and y). You can substitute other values, e.g. by calling
look(1001,-1)
> x = 4 y = 10 z = 0 a = 8 b = 20 c = 160
While the values of a and b change during the execution of look,
the variables x and y retain their old values.
> x = 4 y = 10 z = 160
> # Once the above question is answered I think this will have the same
> # logic.
I've tried my best
Regards, Gregor
> 
> Thanks a lot for this "magic" example.
> With warm regards,
> -Payal
> 
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