Nested loops confusion

[Matthew Graham]

Hi,

I expect this is very obvious for anyone who knows what they're doing - 
but I don't understand what's the problem with the following code.  I 
was intending that the program cycle through all i and j (ie. all 
possible (i,j) coordinates, but the output when I run the program shows 
me up to

"1
99
plot 3
1
100
plot 2
done j"

and doesn't perform the print functions for any i > 1.

Help much appreciated! :)

Matt


corna = int(raw_input("CornA? "))
cornb = int(raw_input("CornB? "))
side = int(raw_input("Side? "))
i = 0
j = 0
for i in range(100):
 for j in range(100):
 x = corna + i * side / 100
 y = cornb + j * side / 100
 c = int(x^2 + y^2)
 if  c%3 == 1:
 print i
 print j
 print "plot 1"
 elif  c%3 == 2:
 print i
 print j
 print "plot 2"
 elif  c%3 == 0:
 print i
 print j
 print "plot 3"
 print "done j"
print "Done i"


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Re: Nested loops confusion

[Matthew Graham]

Oops, I forget to reset the j after the inner loop.  Always manage to 
work these things out just after asking for help! ;-)

Matthew Graham wrote:
> Hi,
> 
> I expect this is very obvious for anyone who knows what they're doing - 
> but I don't understand what's the problem with the following code.  I 
> was intending that the program cycle through all i and j (ie. all 
> possible (i,j) coordinates, but the output when I run the program shows 
> me up to
> 
> "1
> 99
> plot 3
> 1
> 100
> plot 2
> done j"
> 
> and doesn't perform the print functions for any i > 1.
> 
> Help much appreciated! :)
> 
> Matt
> 
> 
> corna = int(raw_input("CornA? "))
> cornb = int(raw_input("CornB? "))
> side = int(raw_input("Side? "))
> i = 0
> j = 0
> for i in range(100):
> for j in range(100):
> x = corna + i * side / 100
> y = cornb + j * side / 100
> c = int(x^2 + y^2)
> if  c%3 == 1:
> print i
> print j
> print "plot 1"
> elif  c%3 == 2:
> print i
> print j
> print "plot 2"
> elif  c%3 == 0:
> print i
> print j
> print "plot 3"
> print "done j"
> print "Done i"
> 
> 
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Re: Nested loops confusion

[Matthew Graham]

Thanks very much for the advice, have tidied it up and tested and seems 
to be working as needed.  I'm still not sure what was stopping the inner 
loop from working earlier - but removing the redundancy in "j=0" and so 
on seems to have solved it.

Matt

Dennis Lee Bieber wrote:
>   If that worked, you've got some weird code -- and it isn't what was
> posted... Zeroing "j" does NOTHING, since the for loop assigns all
> values to it, from 0..n-1
> 
>   for loop indices do not need to be pre-initialized.
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