The for statement is used to iterate over a range of values or a sequence. The for loop is executed for each of the items in the range. These values can be either numeric, or, as we shall see in later chapters, they can be elements of a data type like a string, list, or tuple.
With every iteration of the loop, the control variable checks whether each of the values in the range have been traversed or not. When all the items in the range are exhausted, the statements within loop are not executed; the control is then transferred to the statement immediately following the for loop. While using for loop, it is known in advance the number of times the loop will execute. The flowchart depicting the execution of a for loop is given in Figure.
Flow chart of for loop
(A) Syntax of the For Loop
(B) The Range() Function
The range() is a built-in function in Python. Syntax of range() function is:
range([start], stop[, step])
It is used to create a list containing a sequence of integers from the given start value upto stop value (excluding stop value), with a difference of the given step value. We will learn about functions in the next chapter. To begin with, simply remember that function takes parameters to work on. In function range(), start, stop and step are parameters.
The start and step parameters are optional. If start value is not specified, by default the list starts from 0. If step is also not specified, by default the value increases by 1 in each iteration. All parameters of range() function must be integers. The step parameter can be a positive or a negative integer excluding zero.
The function range() is often used in for loops for generating a sequence of numbers.
