The answer the majority of the time is it does not matter. The number of items in the loop (even what one might consider a “large” number of items, say in the thousands) isn’t going to have an impact on the code. Of course, if you identify this as a bottleneck in your situation, by … Read more
drop procedure if exists doWhile; DELIMITER // CREATE PROCEDURE doWhile() BEGIN DECLARE i INT DEFAULT 2376921001; WHILE (i <= 237692200) DO INSERT INTO `mytable` (code, active, total) values (i, 1, 1); SET i = i+1; END WHILE; END; // CALL doWhile();
while runs the loop while the condition is true. until runs the loop until the condition is true (i.e. while the condition is false). See http://www.gnu.org/software/bash/manual/bashref.html#Looping-Constructs.
Starting Python 3.8, and the introduction of assignment expressions (PEP 572) (:= operator), it’s now possible to capture an expression value (here sys.stdin.read(1)) as a variable in order to use it within the body of while: while (i := sys.stdin.read(1)) != ‘\n’: do_smthg(i) This: Assigns sys.stdin.read(1) to a variable i Compares i to \n If … Read more
$ perl -MO=Deparse -e ‘while () { }’ while (1) { (); } -e syntax OK It seems that while () {} and while (1) {} are equivalent. Also note that empty parens* are inserted in the empty block. Another example of pre-defined compiler behaviour: $ perl -MO=Deparse -e ‘while (<>) { }’ while (defined($_ … Read more
An off-by-one error is for example when you intend to perform a loop n times and write something like: for (int i = 1; i < n; ++i) { … } or: for (int i = 0; i <= n; ++i) { … } In the first case the loop will be executed (n – … Read more
Now someone told me that this is not very good programming because I use the return statement inside a loop and this would cause garbage collection to malfunction. That’s incorrect, and suggests you should treat other advice from that person with a degree of skepticism. The mantra of “only have one return statement” (or more … Read more
while file.readline().startswith(“#”): pass This uses the pass statement : The pass statement does nothing. It can be used when a statement is required syntactically but the program requires no action. http://www.network-theory.co.uk/docs/pytut/passStatements.html