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Chapter 8 - Strings and Text Editing (Python)

Here's a concise walkthrough of the main ideas in Chapter 8, each with a small example.

String literals and escape sequences​

You can write strings with single or double quotes, and use backslash escape sequences like \', \", \n, \t, and \\ for special characters.

Example:

spam = "That is Alice's cat."
spam2 = 'Say hi to Bob\'s mother.'
print("Hello there!\nHow are you?\nI\'m doing fine.")

Raw strings​

Prefix with r to make a raw string, where backslashes are not treated as escapes; useful for paths and regex patterns.

Example:

print(r'The file is in C:\Users\Alice\Desktop')
print(r'Hello...\n\n...world!')  # backslashes shown literally

Multiline strings and comments​

Triple quotes (''' or """) create multiline strings that can contain quotes and newlines; they're also often used as multiline comments or docstrings.

Example:

print('''Dear Alice,

Can you feed Eve's cat this weekend?

Sincerely,
Bob''')

"""This is a test program.
Written by Alice.
This can serve as a multiline comment or docstring."""

String indexing and slicing​

Strings support indexing and slicing like lists; indexes start at 0, negative indexes count from the end, and slices use [start:end] with end excluded.

Example:

greeting = 'Hello, world!'
print(greeting[0])      # 'H'
print(greeting[-1])     # '!'
print(greeting[0:5])    # 'Hello'
print(greeting[7:-1])   # 'world'
print(greeting[7:])     # 'world!'

in and not in with strings​

You can test if a substring appears inside another string using in / not in.

Example:

print('Hello' in 'Hello, world')      # True
print('HELLO' in 'Hello, world')      # False
print('cats' not in 'cats and dogs')  # False

f-strings (formatted string literals)​

Prefix a string with f and use {} to embed expressions directly, instead of manual concatenation.

Example:

name = 'Al'
age = 4000
print(f'My name is {name}. I am {age} years old.')
print(f'In ten years I will be {age + 10}')

Literal braces:

print(f'{{name}}')  # prints {name}

Older formatting: %s and str.format()​

Before f-strings, %s interpolation and .format() were used to insert values into strings.

Example with %s:

name = 'Al'
age = 4000
print('My name is %s. I am %s years old.' % (name, age))

Example with format():

print('My name is {}. I am {} years old.'.format(name, age))
print('{1} years ago, {0} was born and named {0}.'.format(name, age))

Changing case: upper(), lower(), isupper(), islower()​

upper() / lower() return new strings; isupper() / islower() check if the string has letters and all are in that case.

Example:

spam = 'Hello, world!'
print(spam.upper())        # 'HELLO, WORLD!'
print(spam.lower())        # 'hello, world!'
print('HELLO'.isupper())   # True
print('abc123'.islower())  # True

Case-insensitive check:

print('How are you?')
feeling = input()
if feeling.lower() == 'great':
    print('I feel great too.')
else:
    print('I hope the rest of your day is good.')

isX checks: isalpha(), isalnum(), isdecimal(), isspace(), istitle()​

These methods return True/False depending on what characters the string contains and whether it's title-cased.

Example:

print('hello'.isalpha())          # True
print('hello123'.isalnum())       # True
print('123'.isdecimal())          # True
print('   '.isspace())            # True
print('This Is Title Case'.istitle())  # True

Simple input validation:

while True:
    print('Enter your age:')
    age = input()
    if age.isdecimal():
        break
    print('Please enter a number for your age.')

while True:
    print('Select a new password (letters and numbers only):')
    password = input()
    if password.isalnum():
        break
    print('Passwords can only have letters and numbers.')

startswith() and endswith()​

Check if a string begins or ends with a given substring.

Example:

s = 'Hello, world!'
print(s.startswith('Hello'))   # True
print(s.endswith('world!'))    # True
print('abc123'.startswith('abc'))  # True

Joining and splitting strings​

  • 'sep'.join(list_of_strings) builds one string from many.
  • 'text'.split() splits into words on whitespace by default, or on a given delimiter.

Examples:

print(', '.join(['cats', 'rats', 'bats']))  # 'cats, rats, bats'
print(' '.join(['My', 'name', 'is', 'Simon']))  # 'My name is Simon'

print('My name is Simon'.split())          # ['My', 'name', 'is', 'Simon']
print('MyABCnameABCisABCSimon'.split('ABC'))  # ['My', 'name', 'is', 'Simon']

Split multiline string into lines:

spam = '''Dear Alice,
There is a milk bottle in the fridge
that is labeled "Milk Experiment."

Please do not drink it.
Sincerely,
Bob'''
lines = spam.split('\n')

Justifying and centering text: rjust(), ljust(), center()​

These methods pad strings to a given total width, optionally with a fill character.

Example:

print('Hello'.rjust(10))          # '     Hello'
print('Hello'.ljust(10, '-'))     # 'Hello-----'
print('Hello'.center(20, '='))    # '=======Hello========'

Stripping whitespace or specific characters: strip(), lstrip(), rstrip()​

Remove whitespace (default) or specified characters from the ends of a string.

Example:

spam = '   Hello, World   '
print(spam.strip())   # 'Hello, World'
print(spam.lstrip())  # 'Hello, World   '
print(spam.rstrip())  # '   Hello, World'

Strip specific characters:

spam = 'SpamSpamBaconSpamEggsSpamSpam'
print(spam.strip('ampS'))  # 'BaconSpamEggs'

Unicode code points: ord() and chr()​

ord() gives the integer code point for a character; chr() does the reverse.

Example:

print(ord('A'))   # 65
print(ord('!'))   # 33
print(chr(65))    # 'A'
print(chr(ord('A') + 1))  # 'B'

Clipboard access with pyperclip​

The third-party pyperclip module provides copy() and paste() to interact with the system clipboard.

Example:

import pyperclip

pyperclip.copy('Hello, world!')
text = pyperclip.paste()
print(text)  # 'Hello, world!'

Alternating-case program:

import pyperclip

text = pyperclip.paste()
alt_text = ''
make_upper = False

for ch in text:
    alt_text += ch.upper() if make_upper else ch.lower()
    make_upper = not make_upper

pyperclip.copy(alt_text)
print(alt_text)

Project: bulletPointAdder (add bullets to lines)​

Reads text from clipboard, adds * to each line, writes back to clipboard using split('\n') and '\n'.join(...).

Core version:

import pyperclip

text = pyperclip.paste()
lines = text.split('\n')
for i in range(len(lines)):
    lines[i] = '* ' + lines[i]
text = '\n'.join(lines)
pyperclip.copy(text)

Project: Pig Latin translator​

Transforms each word into Pig Latin while preserving punctuation and capitalization using string methods like split, isalpha, isupper, istitle, lower, join.

Very compact sketch:

print('Enter the English message to translate into pig latin:')
message = input()
VOWELS = ('a', 'e', 'i', 'o', 'u', 'y')
pig_latin = []

for word in message.split():
    prefix_non = ''
    while len(word) > 0 and not word[0].isalpha():
        prefix_non += word[0]
        word = word[1:]
    if len(word) == 0:
        pig_latin.append(prefix_non)
        continue

    suffix_non = ''
    while not word[-1].isalpha():
        suffix_non = word[-1] + suffix_non
        word = word[:-1]

    was_upper = word.isupper()
    was_title = word.istitle()
    word = word.lower()

    prefix_cons = ''
    while len(word) > 0 and word[0] not in VOWELS:
        prefix_cons += word[0]
        word = word[1:]

    if prefix_cons:
        word = word + prefix_cons + 'ay'
    else:
        word = word + 'yay'

    if was_upper:
        word = word.upper()
    elif was_title:
        word = word.title()

    pig_latin.append(prefix_non + word + suffix_non)

print(' '.join(pig_latin))

Overall idea of the chapter​

Chapter 8 shows Python's rich set of string methods for searching, formatting, splitting, joining, and transforming text. F-strings are the modern way to embed values, and mastering these tools lets you process text data efficiently — from simple case conversion to full Pig Latin translation.