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Exercise 1: Playing around 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) "I would like a " + s2

b) 3 * s1 + s2

c) s2[2:4]

d) s1[3] + s2[3:] + s2[-1]

e) "-".join(s2.split("n"))

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) "nana"

b) "apple banana! apple banana! apple banana!"

c) ["b", "n", "n", "!"]

Exercise 2: Looping through strings

Show the output that would be generated by each of the following program fragments:

a) for ch in "banana":
       print(ch)

b) for word in "apple banana cat dog elephant...".split():
       print(word)

c) for s in "apple".split("p"):
       print(s)

d) msg = "" # accumulate a string in msg
   for s in "apple banana cat".split("a"):
       msg = msg + s
   print(msg)

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Exercise 3: Acronym-ification

An acronym is a word formed by taking the first letters of the words in a phrase and making a word from them. For example, RAM is an acronym for “random access memory”.

Write a program that allows the user to type in a phrase and then outputs the acronym for that phrase. The acronym should be all uppercase, even if the words in the phrase are not capitalized.

Hint: You should use the accumulator pattern to build up the resulting string.

Exercise 4: Word statistics

Write a program that asks the user to type in a sentence, and outputs the number of words in that sentence.

Here is an example interaction:

Please enter a sentence: Apple banana cat dog elephant fish giraffe.

That sentence has 7 words.

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Exercise 5: Looping through strings, part 2

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

msg = ""
for ch in "banana":
    msg = msg + chr(ord(ch) + 1)
print(msg)

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