Software tutorial/Loops

Looping with a for loop is easy when you know how many iterations will be required.

MATLAB

Python

The simplest loop can be written: for k = 0:4 disp(k) end and the output should be: 0 1 2 3 4 The reason why this works is that instruction k = 0:4 creates a vector, starting at 0 and ending at 4, in steps of 1.0. You can verify this in MATLAB: >> k = 0:4 k = 0 1 2 3 4 Try looping and printing with these vectors. What is the output you expect when: >> j = 0:0.2:5 >> i = 10:-2:-10 If you need help in MATLAB, you can type, for example: help colon and it will show you how to use the colon operator.

The simplest loop can be written: for k in range(5): print(k) and the output should be: 0 1 2 3 4 Why does the output not include the number 5? In Python, you can always check what a function does by using the help command. For example: >>> help(range) range([start,] stop[, step]) -> list of integers Return a list containing an arithmetic progression of integers. range(i, j) returns [i, i+1, i+2, ..., j-1]; start (!) defaults to 0. When step is given, it specifies the increment (or decrement). For example, range(4) returns [0, 1, 2, 3]. The end point is omitted! These are exactly the valid indices for a list of 4 elements. This shows you that the only input required to the range() function is the stop input - the other inputs, [start] and [step] have square brackets in the HELP text, indicating that they are optional inputs. Using the above HELP text, what would you expect in Python if you typed: >>> range(1,5) >>> range(10, -10, -2)