Home > Articles > Programming > Python

  • Print
  • + Share This
This chapter is from the book

4.11. Exercises


Processes versus Threads. What are the differences between processes and threads?


Python Threads. Which type of multithreaded application will tend to fare better in Python, I/O-bound or CPU-bound?


Threads. Do you think anything significant happens if you have multiple threads on a multiple CPU system? How do you think multiple threads run on these systems?


Threads and Files.

  1. Create a function that obtains a byte value and a filename (as parameters or user input) and displays the number of times that byte appears in the file.
  2. Suppose now that the input file is extremely large. Multiple readers in a file is acceptable, so modify your solution to create multiple threads that count in different parts of the file such that each thread is responsible for a certain part of the file. Collate the data from each thread and provide the correct total. Use the timeit module to time both the single- threaded new multithreaded solutions and say something about the difference in performance, if any.


Threads, Files, and Regular Expressions. You have a very large mailbox file—if you don’t have one, put all of your e-mail messages together into a single text file. Your job is to take the regular expressions you designed earlier in this book that recognize e-mail addresses and Web site URLs and use them to convert all e-mail addresses and URLs in this large file into live links so that when the new file is saved as an .html (or .htm) file, it will show up in a Web browser as live and clickable. Use threads to segregate the conversion process across the large text file and collate the results into a single new .html file. Test the results on your Web browser to ensure the links are indeed working.


Threads and Networking. Your solution to the chat service application in the previous chapter required you to use heavyweight threads or processes as part of your solution. Convert your solution to be multithreaded.


*Threads and Web Programming. The Crawler application in Chapter 10, “Web Programming: CGI and WSGI,” is a single-threaded application that downloads Web pages. It would benefit from MT programming. Update crawl.py (you could call it mtcrawl.py) such that independent threads are used to download pages. Be sure to use some kind of locking mechanism to prevent conflicting access to the links queue.


Thread Pools. Instead of a producer thread and a consumer thread, change the code for prodcons.py, in Example 4-12 so that you have any number of consumer threads (a thread pool) which can process or consume more than one item from the Queue at any given moment.


Files. Create a set of threads to count how many lines there are in a set of (presumably large) text files. You can choose the number of threads to use. Compare the performance against a single-threaded version of this code. Hint: Review the exercises at the end of the Chapter 9, in Core Python Programming or Core Python Language Fundamentals.


Concurrent Processing. Take your solution to Exercise 4-9 and adopt it to a task of your selection, for example, processing a set of e-mail messages, downloading Web pages, processing RSS or Atom feeds, enhancing message processing as part of a chat server, solving a puzzle, etc.


Synchronization Primitives. Investigate each of the synchronization primitives in the threading module. Describe what they do, what they might be useful for, and create working code examples for each.

The next couple of exercises deal with the candy.py script featured in Example 4-11.


Porting to Python 3. Take the candy.py script and run the 2to3 tool on it to create a Python 3 version called candy3.py.


The threading module. Add debugging to the script. Specifically, for applications that use semaphores (whose initial value is going to be greater than 1), you might need to know exactly the counter’s value at any given time. Create a variation of candy.py, perhaps calling it candydebug.py, and give it the ability to display the counter’s value. You will need to look at the threading.py source code, as alluded to earlier in the CORE TIP sidebar. Once you’re done with the modifications, you can alter its output to look something like the following:

$ python candydebug.py
starting at: Mon Apr  4 00:24:28 2011
THE CANDY MACHINE (full with 5 bars)!
Buying candy... inventory: 4
Refilling candy... inventory: 5
Refilling candy... full, skipping
Buying candy... inventory: 4
Buying candy... inventory: 3
Refilling candy... inventory: 4
Buying candy... inventory: 3
Buying candy... inventory: 2
Buying candy... inventory: 1
Buying candy... inventory: 0
Buying candy... empty, skipping
all DONE at: Mon Apr  4 00:24:36 2011
  • + Share This
  • 🔖 Save To Your Account

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information

To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.


Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.


If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information

Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.


This site is not directed to children under the age of 13.


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information

If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information

Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents

California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure

Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact

Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice

We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020