Modulo for dummies
by Antoine  Categories : Programming
The modulo is a mathematical operation useful as a programming operator when one needs to repeat an event every n times. Written «%»), the modulo actually returns the rest of an euclidean division.
A common application for it is to make a treatment for even iterations in a loop, and another one for odds. For example, this is can be useful for applying a conversationlike style in a comment flow like in my site. A "left to right" style is applied on odd iterations, and a "righ to left" on even iterations. But it can be useful for many other needs.
Examples
 12 / 6 == 2, remains 0, so 12 % 6 == 0.
Another method, with the same operation, the goal is to "remove" as many times as possible "2" from the figure "7" to get as close as possible to zero : 7 > 5 > 3 > 1 We can remove three times "2" from it, but we can't get lower than... 1, the remainder, and by the way the result of our modulo.

7 / 2 == 3, 1 remains, so 7 % 2 = 1

Same method with 8 % 3 = 8 > 5 > 2
Code
PHP
$i = 0;
while ($i < 10) {
$mod = $i % 3;
echo $mod;
$i++;
}
Ouput
0120120120
Python
Same example as above
i = 0
while (i < 10):
mod = i % 3
print(mod)
i += 1
Python output
0
1
2
0
1
2
0
1
2
0
Another example
list = ["com1", "com2", "com3", "com4"]
for i in range(len(list)): # Iterate over list indexes
if i % 2 == 1:
print(f'{list[i]} > {i} % 2 > 1 > odd')
else:
print(f'{list[i]} > {i} % 2 > 0 > even')
Python output
com1 > 0 % 2 > 0 > even
com2 > 1 % 2 > 1 > odd
com3 > 2 % 2 > 0 > even
com4 > 3 % 2 > 1 > odd
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