[Solved] Can someone explain why the outputs are different here ?

Question

Check this code,
https://code.sololearn.com/cXs6wY2auuLV/?ref=app
For the first loop i assign new values to row and col using a,b = val1, val2
For the second loop I use
a = val1
b = val2
For some unknown reasons the outputs are different and from what the output is I see that it skips some iterations in between.
I really don't understand why this is happening.
Any answer is appreciated, thanks :)

Answer 1

I'm just waiting for some python expert to notice this

Answer 2

In the first example, the values of "row" and "col" are the same for "data[row][col][0]" and "data[row][col][1]". This is because "row,col = ..." reassigns them simultaneosly.

In the second example, the value of "row" in "data[row][col][1]" is different than the one used in "data[row][col][0]" because you're reassigning "row" in line 23. Therefore, in line 24 you use the new value, not the old one.

Answer 3

Diego oh .... How could I have not seen that, thanks.

Answer 4

~ swim ~ (not available on messanger) the algorithm works fine on both now, but now I'm left with the above problem, why does that even happen when both are the same thing.

Answer 5

~ swim ~ (not available on messanger) the list in the program above is generated by that algorithm, in the function I named tracePath() all the time I thought the bug was in the search function but then I realized that it was the while loop in the output function which was going wrong.

Answer 6

This problem arissed when I was implementing A* algorithm, I made the c++ version then tried on python, and it took me more than 6 hours to figure out the bug was in the last loop.