Book Image

Dancing with Python

By : Robert S. Sutor
Book Image

Dancing with Python

By: Robert S. Sutor

Overview of this book

Dancing with Python helps you learn Python and quantum computing in a practical way. It will help you explore how to work with numbers, strings, collections, iterators, and files. The book goes beyond functions and classes and teaches you to use Python and Qiskit to create gates and circuits for classical and quantum computing. Learn how quantum extends traditional techniques using the Grover Search Algorithm and the code that implements it. Dive into some advanced and widely used applications of Python and revisit strings with more sophisticated tools, such as regular expressions and basic natural language processing (NLP). The final chapters introduce you to data analysis, visualizations, and supervised and unsupervised machine learning. By the end of the book, you will be proficient in programming the latest and most powerful quantum computers, the Pythonic way.
Table of Contents (29 chapters)
Part I: Getting to Know Python
PART II: Algorithms and Circuits
PART III: Advanced Features and Libraries
Other Books You May Enjoy
Appendix C: The Complete UniPoly Class
Appendix D: The Complete Guitar Class Hierarchy
Appendix F: Production Notes

3.3 The joy of O(1)

How long should it take for len to compute the length of the list? One way is to iterate through the list:

  1. Initialize a counter to 0.
  2. If the list is not empty, go to the first item and add one to the counter. Otherwise, return the value of the counter, which is 0.
  3. Try going to the next item. If it is not present, we have reached the end and return the counter. Otherwise, go to the item and increment the counter.
  4. Go back to the previous step and repeat until we are finished.

There is a computing time overhead in moving from item to item and incrementing the counter. Let’s call this C. If our list has n items, then

time to compute the length by this method ≤ C × n.

If your computer is faster than mine, your C might be smaller. C also depends on the implementation of lists and Python itself.

This algorithm is O(n): its time is proportional...