Strings

8.1 INTRODUCTION

In Chapter 5, students were introduced to the concept of sequences, which are orderly collections of items where each item is indexed by an integer. Python provides several sequence data types, including strings, lists, and tuples. Additionally, a different data type called 'Dictionary' was introduced, which falls under the category of mappings rather than sequences. This chapter focuses exclusively on strings, exploring their properties, operations, and methods in detail. While lists, tuples, and dictionaries were briefly introduced earlier, their detailed study is reserved for subsequent chapters: lists in Chapter 9, and tuples and dictionaries in Chapter 10. Understanding strings is fundamental because they are widely used in programming for storing and manipulating textual data. This chapter will build upon the foundational knowledge of sequences and provide a comprehensive overview of string handling in Python.

• Sequences are ordered collections indexed by integers.
• Python sequence data types include strings, lists, and tuples.
• Dictionaries are mapping types, not sequences.
• This chapter focuses on strings in detail.
• Lists, tuples, and dictionaries are covered in later chapters.
• Strings are essential for handling textual data in programming.
• 📌 Sequence: An ordered collection of items indexed by integers.
• 📌 String: A sequence of Unicode characters enclosed in quotes.
• 📌 Dictionary: A mapping data type associating keys with values.

8.2 STRINGS

A string in Python is a sequence made up of one or more Unicode characters. These characters can be letters, digits, whitespace, or any other symbols. Strings are created by enclosing characters within single quotes (' '), double quotes (" "), or triple quotes (''' ''' or """ """). Triple quotes allow strings to span multiple lines, making them useful for longer text blocks or documentation strings. Python does not have a separate character data type; a string of length one is considered a character. For example, the variables str1, str2, str3, and str4 can all hold the same string value 'Hello World!' when enclosed in different types of quotes. Using triple quotes, strings can be extended over multiple lines without the need for explicit newline characters. This flexibility in string declaration is important for writing readable and maintainable code. Strings are immutable sequences, meaning their contents cannot be changed once created, a concept explored further in section 8.2.2.

• Strings are sequences of one or more Unicode characters.
• Characters can be letters, digits, whitespace, or symbols.
• Strings can be enclosed in single, double, or triple quotes.
• Triple quotes allow multi-line strings.
• Python has no separate character data type; single-character strings are used.
• Strings are immutable sequences.
• 📌 Unicode: A standard for encoding characters from all writing systems.
• 📌 Immutable: Cannot be changed after creation.