2.12 Write Python expressions corresponding to these statements: (a) The sum of the first seven positive integers (b) The average age of Sara (age 65), Fatima (57), and Mark (age 45) (c) 2 to the 20th power (d) The number of times 61 goes into 4356 (e) The remainder when 4365 is divided by 61 2.13 Start by evaluating, in the interactive shell, the assignment: >>> s1 = '-' >>> s2 = '+' Now write string expressions involving s1 and s2 and string operators + and * that evaluate to: (a) '-+' (b) '+' (c) '+' (d) '++' (e) '+++++++++++' (f) '++++++++++++++++++++' Try to make your string expressions as succinct as you can. 2.14 Start by running, in the shell, the following assignment statement: >>> s = 'abcdefghijklmnopqrstuvwxyz' Now write expressions using string s and the indexing operator that evaluate to 'a', 'c', 'z', 'y', and 'q'. 2.15 Start by executing s = 'goodbye' Then write a Boolean expression that check whether: (a) The first character of string s is 'g' (b) The seventh character of s is g (c) The first two characters of s are g and a (d) The next to last character of s is x (e) The midle character of s is d (f) The first and last characters of string s are equal (g) The last 4 characters of string s match the string 'tion' Note: These seven statements should evaluate to True, False, False, False, True, False, and False, respectively. 2.16 Write the corresponding Python assignment statements: (a) Assign 6 to variable a and 7 to variable b. (b) Assign to variable c the average of variables a and b. Chapter 2 Exercises 49 (c) Assign to variable inventory the list containing strings 'paper', 'staples', and 'pencils'. (d) Assign to variables first, middle and last the strings 'John', 'Fitzgerald', and 'Kennedy'. (e) Assign to variable fullname the concatenation of string variables first, middle, and last. Make sure you incorporate blank spaces appropriately.