#### Overview of this book

Choosing the right data structure is pivotal to optimizing the performance and scalability of applications. This new edition of Hands-On Data Structures and Algorithms with Python will expand your understanding of key structures, including stacks, queues, and lists, and also show you how to apply priority queues and heaps in applications. You’ll learn how to analyze and compare Python algorithms, and understand which algorithms should be used for a problem based on running time and computational complexity. You will also become confident organizing your code in a manageable, consistent, and scalable way, which will boost your productivity as a Python developer. By the end of this Python book, you’ll be able to manipulate the most important data structures and algorithms to more efficiently store, organize, and access data in your applications.
Preface
Free Chapter
Python Data Types and Structures
Introduction to Algorithm Design
Algorithm Design Techniques and Strategies
Stacks and Queues
Trees
Heaps and Priority Queues
Hash Tables
Graphs and Algorithms
Searching
Sorting
Selection Algorithms
String Matching Algorithms
Other Books You May Enjoy
Index

# Symbol tables

Symbol tables are used by compilers and interpreters to keep track of the symbols and different entities, such as objects, classes, variables, and function names, that have been declared in a program. Symbol tables are often built using hash tables since it is important to efficiently retrieve a symbol from the table.

Let’s look at an example. Suppose we have the following Python code in the `symb.py` file:

``````    name = "Joe"
age = 27
``````

Here, we have two symbols, `name` and `age`. Each symbol has a value; for example, the `name` symbol has the value `Joe`, and the `age` symbol has the value `27`. A symbol table allows the compiler or the interpreter to look up these values. So, the `name` and `age` symbols become keys in the hash table. All of the other information associated with them becomes the `value` of the symbol table entry.

In compilers, symbol tables can have other symbols as well, such as functions and class names. For example, the `greet()` function...