Breaking Out of Nested Loops

1. r = 10
2. n = 240
3. for x in range(r):
4. for y in range(r):
5. for z in range(r):
6. # Start reading here
7. if x * y * z == n:
8. print(x,y,z)
9. # 5 6 8
10. break
11. else:
12. continue
13. break
14. else:
15. continue
16. break

1. const int r(10 );
2. const int n(240);
3. for ( int x = 0; x < r; x++ ) {
4. for ( int y = 0; y < r; y++ ) {
5. for ( int z = 0; z < r; z++ ) {
6. // Start reading here
7. if ( x * y * z == n ) {
8. qDebug() << x << y << z;
9. goto finished;
10. }
11. }}} finished:

Read as:

• if [ expression is true ]
• print x y z
• 'break'out of loop z [ ignore the else ]
• 'break'out of loop y [ ignore the else ]
• 'break'out of loop x.

• if [ expression is true ]
• debug out x y z
• and goto finished [ label ]

Benefits:

• In python, you can place an "else" statement after a loop ( "for" or "while" ) which gets called if the loop exits without a 'break' statement. This is a novell construct absent in c++."

• This code, is clean, and in this particular case, no extra indentation was needed.
• the "goto" label is particularly descriptive: "[ I am finished ] goto finish line."

Drawbacks:

• This "else" feature is esoteric and unknown towards most Python developers.
• The "else" mistakenly seems like the continuation to the "if" statement above.
• This feature does not exist in any other language, making this a non-transferable idiom.
• Indentation structure is bumpy and disorienting.

• None.