for Loops – Ken Lambert

Python

Java

There is just one type of for loop, which visits each element in an iterable object, such as a string or list.

Form:

for <variable> in <iterable>:
    <statement>
    …
    <statement>

Example:

for s in aListOfStrings:
print(s)

The variable picks up the value of each element in the iterable object and is visible in the loop body.

The statements in the loop body are marked by indentation.

Simple count-controlled loops that iterate through a range of integers have three forms:

for <variable> in range(<upper bound>):
    <statement>
    …
    <statement>

for <variable> in range(<lower bound>, <upper bound>):
    <statement>
    …
    <statement>

for <variable> in range(<lower bound>, <upper bound>, <step value>):
    <statement>
    …
    <statement>

There are two types, a loop for visiting each element in an iterable object, and a loop with the same behavior as a while loop.

Form of the first type (also called an enhanced for loop):

for (<type> <variable> : <iterable>){
    <statement>
    …
    <statement>
}

Example:

for (String s : aListOfStrings){
System.out.println(s);
}

The variable picks up the value of each element in the iterable object and is visible in the loop body.

The statements in the loop body are marked by curly braces ({}). When there is just one statement in the loop body, the braces may be omitted.

Form of the second type:

for (<initializer>; <continuation>; <update>){
    <statement>
    …
    <statement>
}

Example:

for (int i = 1; i <= 10; i++){
System.out.println(i);
}

This loop has the same behavior as the following while loop:

int i = 1;
while (i <= 10){
System.out.println(i);
i++;
}