Counting loop

In e.g. C/C++, C# and Java a loop controlled by a counter is implemented without problems:

Example:

for(int i = 0; i <= 3 ; i++)           // for(<initialization>;<condition>;<increment>
{
    System.out.println(i + ". Item");  // Java syntax
}

Output:

0. Item
1. Item
2. Item
3. Item 

In contrary in Python the For loop iterates over a list:

for i in list:      # Python syntax
    ...

A special counting list does not exist in Python!

Therefore for this purpose at first a list with numbers has to be created:

list = [0,1,2,3]
for i in list:
    print(str(i) + ". Item")

The output will be the same as shown above:

0. Item
1. Item
2. Item
3. Item 

Function range()

To simplify the creation of the required list, the range() function is used.

list = range(4)
for i in list:
    print(str(i) + ". Item")

or directly

for i in range(4):
    print(str(i) + ". Item")
    
    
    

Further use of range()

>>> range(10) 
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

The number passed as a parameter is never part of the list; it represents the length of the list starting with 0.

The list can also begin with a number other than 0. The function then receives the start value as the first parameter and the end value as the second parameter.

>>> range(5, 10)
[5, 6, 7, 8, 9]

The step length can also be passed as a third parameter:

>>> range(0, 10, 3)
[0, 3, 6, 9]

Negative information is also possible:

>>> range(-10, -100, -30) 
[-10, -40, -70]