Exercise 3.3.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 s 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.
Exercise 3.4.A function object is a value you can assign to a variable or pass as an argument. For example, do twice is a function that takes a function object as an argument and calls it twice:
def do_twice(f): f() f()
Here’s an example that uses do_twiceto call a function named print_spamtwice.
def print_spam(): print 'spam' do_twice(print_spam)
- Type this example into a script and test it.
- Modify do_twiceso that it takes two arguments, a function object and a value, and calls the function twice, passing the value as an argument.
- Write a more general version of print_spam,, called print_twice, that takes a string as a parameter and prints it twice.
- Use the modiﬁed version of do_twiceto call print_twicetwice, passing 'spam' as an argument.
- Deﬁne a new function called do_fourthat takes a function object and a value and calls the function four times, passing the value as a parameter. There should be only two statements in the body of this function, not four.
Exercise 3.5.This exercise can be done using only the statements and other features we have learned so far.
1.Write a function that draws a grid like the following:
Hint: to print more than one value on a line, you can print a comma-separated sequence:
print '+', '-'
If the sequence ends with a comma, Python leaves the line unfinished, so the value printed next appears on the same line.
The output of these statements is '+-'.
A printstatement all by itself ends the current line and goes to the next line.
2. Write a function that draws a similar grid with four rows and four columns.
Solution: http: // thinkpython. com/ code/ grid. py . Credit: This exercise is based on an exercise in Oualline, Practical C Programming, Third Edition, O’Reilly Media, 1997.