Exercises

Exercise 1

Python provides a built-in function called len that returns the length of a string, so the value of len('allen') is 5.

Write a function named right_justify" that takes a string named word as a parameter and prints the string with enough leading spaces so that the last letter of the string is in column 70 of the display.

>>> right_justify('allen') 
                                                     allen

Answer

def rightJustify(word):
    print(' ' * (70 - len(s)) + word)

Exercise 2

This exercise can be done using only the statements and other features we have learned so far.

1. Write a function two_by_two_grid that draws a grid like the following:

+ - + - +
|   |   |
+ - + - +
|   |   |
+ - + - +

Hint: to print more than one value on a line, you can print a comma-separated sequence like print('+', '-').

In order to build a string spanning several lines, we can use the string character '\n' which represents the newline character. The newline character can be embedded in a string, or can be concatenated using the + operator as shown in the following examples.

>>> print('line 1 \nline 2')
 line 1 
 line 2 
>>> print('line 1' + '\n' + 'line 2')
 line 1 
 line 2
>>> 

A print statement all by itself ends the current line and goes to the next line.

Answer

def two_by_two_grid():
    print('+', '-', '+', '-', '+')
    print('|', ' ', '|', ' ', '|')
    print('+', '-', '+', '-', '+')
    print('|', ' ', '|', ' ', '|')
    print('+', '-', '+', '-', '+')

Note: this is not a very good solution, a better approach is used in the solution for the function four_by_four_grid.

1. Write another function four_by_four_gridto draw a similar grid with four rows and four columns.

Answer

def four_by_four_grid():
    oddLine = '+ - ' * 4 + '+\n'
    evenLine = '|   ' * 4 + '|\n'
    grid = (oddLine + evenLine) * 4 + oddLine
    print(grid)

Note: This solution is better than the one given for the function two_by_two_grid. It is important to familiarise ourselves with manipulating string to build the expected output.

1. Write a more generic function x_by_y_grid(rows, cols) that draws a similar grid with rows rows and cols columns.

Answer

def x_by_y_grid(rows, cols):
    oddLine = '+ - ' * cols + '+\n'
    evenLine = '|   ' * cols + '|\n'
    grid = (oddLine + evenLine) * rows + oddLine
    print(grid)

Note: once we have written the generic function, we can refactor (rewrite) both the two_by_two_grid and four_by_four_gridto functions by calling the x_by_y_grid(rows, cols) function as shown below.

def two_by_two_grid():
    x_by_y_grid(2, 2)
    
def four_by_four_gridto():
    x_by_y_grid(4, 4)