Page 99 - trackpad v5.1 class 8 flipbook
P. 99

ITERATIVE STATEMENTS


                 Iterative statements refer to the statements that are used to repeat a task based on a given
                 condition. These statements are also known as looping statements. An iteration means one pass
                 of a loop.

                 Python provides the following iterative statements:
                 (i)  For loop                   (ii)  While loop




                      Tick ( ) if you know this.

                      ▶  A computer program is a set of instructions known as statements.
                      ▶   A control structure is a programming language construct which affects the flow of the execution
                        of a program.

                 THE for LOOP

                 The for loop is a type of iterative statement that allows the user to repeat a set of statements
                 multiple times until a given condition is falsified. The for loop is commonly used when the number
                 of iterations is known in advance or when iterating over a sequence, such as a list, string, tuple,
                 or a range."
                 The syntax of for loop is as follows:

                 for <counter variable> in range(start, stop, step_size):
                     statements

                 The  range() function  is  an in-built  function  in Python.  This function  generates  a  sequence  of
                 numbers. A sequence is a succession of values bound together by a single name. The range()
                 function is generally used in the for loop to iterate over the sequence of numbers.

                 The general syntax for using the range() function is given below:
                   range(start, stop, step_size): The start specifies the starting point for generating numbers.

                   By default, it starts from 0. The stop specifies the position up to which the numbers are to be
                   generated (last number is not included). The step_size specifies the increment or decrement.
                   By default, the value of the step_size = 1 and numbers are generated with an increment of
                   1. However, we can generate numbers by specifying the value of step_size according to our
                   requirement.

                   range(start, stop): It generates a set of whole numbers starting from ‘start’ to ‘stop–1’.
                   Example: range(3, 9) is equivalent to [3, 4, 5, 6, 7, 8].
                   range(stop): Generates a set of whole numbers starting from 0 to (stop–1).
                   Example: range(6) is equivalent to [0, 1, 2, 3, 4, 5].

                 The start and step_size values are optional in the application of range() function and they can
                 be omitted.



                                                                                        Control Structures in Python  97
   94   95   96   97   98   99   100   101   102   103   104