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Exercise 0: Playing with chr and ord

Show the output that would be generated by the following program fragment:

msg = ""
for ch in "fish":
    newval = ord(ch) + 4
    mystery = chr(newval)
    print(mystery)
    msg += mystery
print(msg)

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Exercise 1: Working with strings

For this exercise, we’ll use the following statements:

s1 = "apple"
s2 = "banana!"

Exercise 1a: from expression to output

Predict the result of evaluating each of the following string expressions.

a) s1.index('a')

b) s2.split('n')

c) len(s2)

d) s1[8 % len(s1)]

Exercise 1b: from output to expression

Build a Python expression that could construct each of the following results by performing string operations on s1 and s2.

s1 = "apple"
s2 = "banana!"

a) ['b', 'n', 'n', '!']

b) 4

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Exercise 2: Basic list operations

For this exercise, we’ll use the following statements:

numbers = [3, 1, 4, 1, 5]
words = ["apple", "banana", "cat", "dog", "elephant"]

Predict the result of evaluating each of the following list expressions.

a) numbers[-1]

b) words[1:4]

c) words[1] + words[2]

d) len(numbers)

e) numbers + words

f) 2 * numbers + words

g) for word in words:
       print(word[:3])

Exercise 3: Going backwards

Write a program to print a sequence of words in reverse order. You cannot use slicing or the existing reverse list method.

(Hint: you should use split to turn the provided string into a list, and use the accumulator pattern to build the resulting list in reversed order. Think carefully about how you can change the typical body of an accumulator loop to put the new value at the beginning of the accumulator variable instead of the end of the variable.)

Here is an example interaction:

Please enter a sequence of words, separated by spaces: apple banana cat dog elephant fish

The sequence reversed:
fish elephant dog cat banana apple

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Exercise 4: for-loop patterns

Write a for loop using the variables numbers and words to generate each output. Think about whether you need the element and/or its index for each loop.

numbers = [3, 1, 4, 1, 5]
words = ["apple", "banana", "cat", "dog", "elephant"]

a) ae
   ba
   ct
   dg
   et

b) 0 apple
   1 banana
   2 cat
   3 dog
   4 elephant

c) 3
    1
     4
      1
       5

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