Book Image

Julia Programming Projects

By : Adrian Salceanu
Book Image

Julia Programming Projects

By: Adrian Salceanu

Overview of this book

Julia is a new programming language that offers a unique combination of performance and productivity. Its powerful features, friendly syntax, and speed are attracting a growing number of adopters from Python, R, and Matlab, effectively raising the bar for modern general and scientific computing. After six years in the making, Julia has reached version 1.0. Now is the perfect time to learn it, due to its large-scale adoption across a wide range of domains, including fintech, biotech, education, and AI. Beginning with an introduction to the language, Julia Programming Projects goes on to illustrate how to analyze the Iris dataset using DataFrames. You will explore functions and the type system, methods, and multiple dispatch while building a web scraper and a web app. Next, you'll delve into machine learning, where you'll build a books recommender system. You will also see how to apply unsupervised machine learning to perform clustering on the San Francisco business database. After metaprogramming, the final chapters will discuss dates and time, time series analysis, visualization, and forecasting. We'll close with package development, documenting, testing and benchmarking. By the end of the book, you will have gained the practical knowledge to build real-world applications in Julia.
Table of Contents (19 chapters)
Title Page
Copyright and Credits
About Packt

Carrying on with the crawler's implementation

So far, your code should look like this:

using HTTP, Gumbo 

const PAGE_URL = "" 
const LINKS = String[] 

function fetchpage(url) 
  response = HTTP.get(url) 
  if response.status == 200 && parse(Int, Dict(response.headers)["Content-Length"]) > 0 

It should be now clear that either the response body or an empty string is returned by the if/else statement. And since this is the last piece of code evaluated inside the fetchpage function, this value also becomes the return value of the whole function.

All good, we can now use the fetchpage function to get the HTML content of the Wikipedia page and store it in the content variable:

content = fetchpage(PAGE_URL)  

If the fetch operation is successful and the content is not an empty string, we can pass the HTML string to Gumbo to construct the DOM. Then, we can loop through all the...