Sometimes we need to iterate over a range of numbers, and it would be quite unpleasant to have to do so by hardcoding the list somewhere. In such cases, the range function comes to the rescue. Let's see the equivalent of the previous snippet of code:

# simple.for.py
for number in range(5): 
    print(number) 

The range function is used extensively in Python programs when it comes to creating sequences: you can call it by passing one value, which acts as stop (counting from 0), or you can pass two values (start and stop), or even three (start, stop, and step). Check out the following example:

>>> list(range(10))  # one value: from 0 to value (excluded)
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> list(range(3, 8))  # two values: from start to stop (excluded)
[3, 4, 5, 6, 7]
>>> list(range(-10, 10, 4))  # three values: step is added
[-10, -6, -2, 2, 6]

For the moment, ignore that we need to wrap range(...) within a list. The range object is a little bit special, but in this case, we're just interested in understanding what values it will return to us. You can see that the deal is the same with slicing: start is included, stop excluded, and optionally you can add a step parameter, which by default is 1.

Try modifying the parameters of the range() call in our simple.for.py code and see what it prints. Get comfortable with it.