Little Sister's Essay
Little Sister's Essay

Little Sister's Essay

Learning Exercise


The str class offers many useful methods for working with and composing strings. These include searching, cleaning, splitting, transforming, translating, and many other techniques.

Strings are immutable sequences of Unicode code points -- individual "characters" or code points (strings of length 1) can be referenced by 0-based index number from the left, or -1-based index number from the right.

Strings can be iterated through using for item in <str> or for index, item in enumerate(<str>) syntax. They can be concatenated using the + operator or via <string>.join(<iterable>) and implement all common sequence operations.

Strings are immutable, meaning the value of a str object in memory cannot change. Functions or methods that operate on a str (like the ones we are learning about here) will return a new instance of that str object instead of modifying the original str.

Following is a small selection of Python string methods. For a complete list, see the str class in the Python docs.

<str>.title() parses a string and capitalizes the first "character" of each "word" found. In Python, this is very dependent on the language codec used and how the particular language represents words and characters. There may also be locale rules in place for a language or character set.

man_in_hat_th = 'ผู้ชายใส่หมวก'
man_in_hat_ru = 'мужчина в шляпе'
man_in_hat_ko = '모자를 쓴 남자'
man_in_hat_en = 'the man in the hat.'

>>> man_in_hat_th.title()

>>> man_in_hat_ru.title()
'Мужчина В Шляпе'

>>> man_in_hat_ko.title()
'모자를 쓴 남자'

>> man_in_hat_en.title()
'The Man In The Hat.'

<str>.endswith(<suffix>) returns True if the string ends with <suffix>, False otherwise.

>>> 'My heart breaks. 💔'.endswith('💔')

>>> 'cheerfulness'.endswith('ness')

# Punctuation is part of the string, so needs to be included in any endswith match.
>>> 'Do you want to 💃?'.endswith('💃')

>> 'The quick brown fox jumped over the lazy dog.'.endswith('dog')

<str>.strip(<chars>) returns a copy of the str with leading and trailing <chars> removed. The code points specified in <chars> are not a prefix or suffix - all combinations of the code points will be removed starting from both ends of the string. If nothing is specified for <chars>, all combinations of whitespace code points will be removed.

# This will remove "https://", because it can be formed from "/stph:". 
>>> ''.strip('/stph:')

# Removal of all whitespace from both ends of the str.
>>> '   🐪🐪🐪🌟🐪🐪🐪   '.strip()

>>> justification = 'оправдание'
>>> justification.strip('еина')

# Prefix and suffix in one step.
>>> 'unaddressed'.strip('dnue')

>>> '  unaddressed  '.strip('dnue ')

<str>.replace(<substring>, <replacement substring>) returns a copy of the string with all occurrences of <substring> replaced with <replacement substring>.

The quote used below is from The Hunting of the Snark by Lewis Carroll

# The Hunting of the Snark, by Lewis Carroll
>>> quote = '''
"Just the place for a Snark!" the Bellman cried,
   As he landed his crew with care;
Supporting each man on the top of the tide
   By a finger entwined in his hair.

"Just the place for a Snark! I have said it twice:
   That alone should encourage the crew.
Just the place for a Snark! I have said it thrice:
   What I tell you three times is true."

>>> quote.replace('Snark', '🐲')
'\n"Just the place for a 🐲!" the Bellman cried,\n   As he landed his crew with care;\nSupporting each man on the top of the tide\n   By a finger entwined in his hair.\n\n"Just the place for a 🐲! I have said it twice:\n   That alone should encourage the crew.\nJust the place for a 🐲! I have said it thrice:\n   What I tell you three times is true."\n'

>>> 'bookkeeper'.replace('kk', 'k k')
'book keeper'


In this exercise you are helping your younger sister edit her paper for school. The teacher is looking for correct punctuation, grammar, and excellent word choice.

You have four tasks to clean up and modify strings.

1. Capitalize the title of the paper

Any good paper needs a properly formatted title. Implement the function capitalize_title(<title>) which takes a title str as a parameter and capitalizes the first letter of each word. This function should return a str in title case.

>>> capitalize_title("my hobbies")
"My Hobbies"

2. Check if each sentence ends with a period

You want to make sure that the punctuation in the paper is perfect. Implement the function check_sentence_ending() that takes sentence as a parameter. This function should return a bool.

>>> check_sentence_ending("I like to hike, bake, and read.")

3. Clean up spacing

To make the paper look professional, unnecessary spacing needs to be removed. Implement the function clean_up_spacing() that takes sentence as a parameter. The function should remove extra whitespace at both the beginning and the end of the sentence, returning a new, updated sentence str.

>>> clean_up_spacing(" I like to go on hikes with my dog.  ")
"I like to go on hikes with my dog."

4. Replace words with a synonym

To make the paper even better, you can replace some of the adjectives with their synonyms. Write the function replace_word_choice() that takes sentence, old_word, and new_word as parameters. This function should replace all instances of the old_word with the new_word, and return a new str with the updated sentence.

>>> replace_word_choice("I bake good cakes.", "good", "amazing")
"I bake amazing cakes."
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