@stephen @cvp
What difference an identation make !

@stephen
Not all the grids are solvables yet, but ....

[[1 4 5 6 7 8 9 2 3]
 [3 6 7 9 1 2 8 5 4]
 [8 9 2 3 5 4 6 1 7]
 [4 1 3 2 8 9 5 7 6]
 [9 2 6 5 3 7 4 8 1]
 [7 5 8 1 4 6 3 9 2]
 [2 7 9 8 6 3 1 4 5]
 [5 3 4 7 9 1 2 6 8]
 [6 8 1 4 2 5 7 3 9]]
0
1

https://www.dropbox.com/sh/3kaz4sibyi6qjba/AAB2JIfc05xaIFj5xlt6Oe3Ta?dl=0

@stephen All is fine now, thank you.

@cvp Great, It'works. Merci les amis ;-)

@cvp OK, I'll check indentation

@cvp I think the errors occurs in line 147, after the loop. This cannot prevent the loop from executing three times.

@stephen and your code runs without errors ! Have you made some change other than translate ?

@stephen Thanks for the translation.

The code on Dropbox stops after one loop. Whith a breakpoint on line 141 and then step by step you will see that the loop is executed only one time, not three as expected. The name error comes because the bypass over the lines 143 and 144 where the variable 'numero_carre_sans_chiffre' is assigned.

@cvp you're right, but the bug remains on my iPad
It's strange that the same code runs without error on your device.
Thanks a lot to you and to @stephen