This article will show you the best way to handle “main” functions in Python.
Python is like a scripting language in that all lines in a Python “module” (a .py file) are executed whenever the file is run. Modules don’t need a “main” function. Consider a module named stuff.py with the following code:
At first glance, we may expect to see two lines printed. However, running more_stuff actually prints three lines:
$ python more_stuff.py
Why did “stuff happened!” get printed twice? Well, when “import stuff” was called, the stuff module was loaded. Whenever a module is loaded, all of its code is executed. The print_stuff function was called at line 4 in the stuff module. Then, it was called again at line 3 in the more_stuff module.
So, how can we avoid this problem? Simple: check the module’s __name__. The __name__ variable (pronounced “dunder name”) is dynamically set to the module’s name. If the module is the main entry point, then __name__ will be set to “__main__”. Otherwise, if the module is simply imported, then it will be set to the module’s filename without the “.py” extension.
Let’s rewrite our modules. Here’s stuff:
if __name__ == '__main__':
And here’s more_stuff:
if __name__ == '__main__':
If we rerun more_stuff, then the line “stuff happened!” will print only once:
$ python more_stuff.py
As a best programming practice, Python modules should not contain any directly-called lines. They should contain only functions, classes, and variable initializations. Anything to be executed as a “main” body should be done after a check for “if __name__ == ‘__main__'”. That way, no rogue calls are made when modules are imported by other modules. The conditional check for __name__ also makes the “main” body clear to the reader.
Some people still like to have a “main” function. That’s cool. Just do it like this:
PyOhio 2019 was one of my favorite conferences, ever. It was my ninth Python conference and my second PyOhio conference. There were so many good things that happened in such short time that, even three weeks later, I’m still processing everything. Here are my reflections on this outstanding conference.
PyOhio 2019 was held in Columbus, Ohio at the Ohio State Union. I really wanted to go because PyOhio 2018 was such a good time, and I started asking my friends in North Carolina if anyone wanted to join me. My friends Rick and Justin all emphatically replied YES! To make traveling more fun, we decided to turn it into a road trip! We dubbed ourselves the “PyCarolinas delegation”, piled into my Chrysler 300, and made the 8-hour drive in good time. Our friend Greg also joined us at PyOhio, though he traveled separately with his wife.
This was the first time I ever did a road trip to a conference. I’m so glad we did it. I felt like I got to spend great quality time with my friends. Many parts of the drive were quite scenic. We also discovered a Beef Jerky Outlet!
At PyOhio 2019, I delivered the holy trifecta of speaking opportunities: a talk, a tutorial, and a lightning talk. I felt both honored and humbled to be chosen for all three.
My talk was entitled Surviving Without Python. I talked about how we can use Python’s principles, projects, and people to inspire us even when we don’t use Python to solve our problems:
My tutorial was entitled Hands-On Web UI Testing. Python’s popularity continues to rise, and many people use it for testing. In my tutorial, I showed how you can develop a simple yet powerful solution with Python, pytest, and Selenium WebDriver to automate Web UI tests. The tutorial project in GitHub contains the code, instructions, and slides.
My lightning talk was announcing PyCarolinas 2020. My friend Calvin and I are teaming up to bring PyCarolinas back! We are targeting June 2020 in Raleigh, NC. Please help us make it happen!
There were so many great talks at PyOhio. Here were a few highlights.
Sprints are a Python conference event in which people work together on open-source projects. Conferences are the perfect time to have sprints because people are both co-located and excited. PyOhio 2019 was actually the first time I attended sprints. There were sprints on both Friday and Saturday nights. Accenture graciously hosted both sprints in their swanky office and provided refreshments.
I went to the sprints both nights with the honest intention to work on stuff. However, I spent the whole time socializing with friends. It was nevertheless time well spent! Many of us went to Jeni’s Splendid Ice Creams after the final sprint, too.
The PyOhio 2019 logo was lit! I joked that I was going to the conference just to get that logo sticker and t-shirt. Some other cool takeaways were the Numerator puzzles and the JP Morgan Chase puzzle blocks.
My sticker game is strong:
My backpack was also a hit!
Food and Drink
I had some good eats while in Columbus. My friend Mason recommended Raising Cane’s, which turned out to be awesome! So many people followed us there, too.
I also hopped an electric scooter to get bubble tea. Those scooters are so much fun. I hadn’t ridden one since PyTexas 2019! (Or maybe PyCon 2019; I don’t remember precisely.)
To relive PyOhio 2018 memories, I went to Eden Burger for a Vegan brunch on Sunday morning with friends! It was delicious and nutritious.
Our friend Greg recommended we visit Brewdog, a renowned Scottish craft brewery with a huge site on the outskirts of Columbus. We took the tour with the “beer school” course, and we stayed for a delicious dinner afterwards. So good, so very good. It was the best way to end the conference!
The best part about PyOhio 2019 was the time I spent with all my friends. I wish I could name everyone here, but there are just too many names. The Python community is the best. Conference friends are real friends. Also, for what it’s worth, they’ve given me the nickname “Pandy.”
My PyOhio 2019 experience can be summarized in one line:
Truth – I went all-in from leaving my house on Friday morning until returning Monday evening. The conference high is very real. My hope is that I’ll get to attend more great conferences like this, and also that I’ll be able to help make PyCarolinas as good as PyOhio!
On August 14, 2019, I teamed up with SmartBear to deliver a one-hour webinar about Web UI testing with Python! It was an honor to work with Nicholas Brown, Digital Marketing Manager for CrossBrowserTesting at SmartBear Software, to make this webinar happen.
In the webinar, I showed how to build a basic Web UI test automation solution using Python, pytest, and Selenium WebDriver. The tutorial covered automating one test, a simple DuckDuckGo search, from inception to automation. It also showed how to use CrossBrowserTesting to scale the solution so that it can run tests on any browser, any platform, and any version in the cloud as a service!
I encourage you to clone the Github repository and try to run the example test on your own! Make sure to get a CrossBrowserTesting trial license so you can try different browsers. You can also try to write new tests of your own. All instructions are in the README. Have fun with it!
After the tutorial, we took questions from the audience. Here are answers to the top questions:
How can we automate UI interactions for CAPTCHA?
CAPTCHA is a feature many websites use to determine whether or not a user is human. Most CAPTCHAs require the user to read obscured text from an image, but there are other variations. By their very nature, CAPTCHAs are designed to thwart UI automation.
When someone asked this question during the webinar, I didn’t have an answer, so I did some research afterwards. Unfortunately, it looks like there’s no easy solution. The best workarounds involve driving apps through their APIs to avoid CAPTCHAs. I also saw some services that offer to solve CAPTCHAs.
Are there any standard Page Object Pattern implementations in Python?
Not really. Mozilla maintains the PyPOM project, but I personally haven’t used it. I like to keep my page objects pretty simple, as shown in the tutorial. I also recommend the Screenplay Pattern, which handles concerns better as test automation solutions grow larger. I’m actually working on a Pythonic implementation of the Screenplay Pattern that I hope to release soon!
How can I run Python tests that use Selenium WebDriver and pytest from Jenkins?
Any major Continuous Integration tool like Jenkins can easily run Web UI tests in any major language. First, make sure the nodes are properly configured to run the tests – they’ll need Python with the appropriate packages. If you plan to use local browsers, make sure the nodes have the browsers and WebDriver executables properly installed. If you plan to use remote browsers (like with CrossBrowserTesting), make sure your CI environment can call out to the remote service. Test jobs can simply call pytest from the command line to launch the tests. I also recommend the “JUnit” pytest option to generate a JUnit-style XML test report because most CI tools require that format for displaying and tracking test results.
How can I combine API and database testing with Web UI testing?
One way to handle API and database testing is to write integration tests separate from Web UI tests. You can still use pytest, but you’d use a library like requests for APIs andSQLAlchemy for databases.
Another approach is to write “hybrid” tests that use APIs and database calls to help Web UI testing. Browsers are notoriously slow compared to direct back-end calls. For example, database calls could pre-populate data so that, upon login, the website already displays stuff to test. Hybrid tests can make tests much faster and much safer.
How can we test mobile apps and browsers using Python?
Even though our tutorial covered desktop-based browser UI interactions, the strategy for testing mobile apps and browsers is the same. Mobile tests need Appium, which is like a special version of WebDriver for mobile features. The Page Object Pattern (or Screenplay Pattern) still applies. CrossBrowserTesting provides mobile platforms, too!
Python is such a popular language for good reason: Its principles are strong. However, if Python is “the second-best language for everything”… that means the first-best is often chosen instead. Oh no! How can Pythonistas survive a project or workplace without our favorite language?
Personally, even though I love Python, I don’t use it daily at my full time job. Nevertheless, Pythonic thinking guides my whole approach to software. I will talk about how the things that make Python great can be applied to non-Python places in three primary ways:
Have you ever discovered a bug in a web app? Yuck! Almost everyone has. Bugs look bad, interrupt the user’s experience, and cheapen the web app’s value. Severe bugs can incur serious business costs and tarnish the provider’s reputation.
So, how can we prevent these bugs from reaching users? The best way to catch bugs is to test the web app. However, web UI testing can be difficult: it requires more effort than unit testing, and it has a bad rap for being flaky.
Never fear! Recently, I teamed up with the awesome folks at TestProject to develop a helpful tutorial that makes web UI test automation easy with the power of Python! The tutorial is named Web Testing Made Easy with Python, Pytest and Selenium WebDriver. It is available for free as a set of TestProject blog articles together with a GitHub example project.
In our tutorial, we will build a simple yet robust web UI test solution using Python, pytest, and Selenium WebDriver. We cover strategies for good test design as well as patterns for good automation code. By the end of the tutorial, you’ll be a web test automation champ! Your Python test project can be the foundation for your own test cases, too.
I personally want to thank TestProject for this collaboration. TestProject provides helpful tools that can supercharge your test automation. They offer a smart test recorder, a bunch of add-ons that act like test case building blocks, an SDK that can make test automation coding easier, and beautiful analytics to see exactly what the tests are doing. Not only is TestProject a cool platform, but the people with whom I’ve worked there are great. Be sure to check it out!
A Twitter friend recently asked me the following question:
I work in a Microsoft shop. We have 40 developers who use .NET (C#). We also have several manual testers and 5 automation engineers who developed our test automation solution in Python. However, our leadership wants to move everything completely to C#.
Would it be better to (a) train 40 .NET developers in Python to use the existing test solution or (b) train the testers in .NET and port the tests to C#?
This is a very tough question. It’s not as simple as asking for the best test automation language because there are people, positions, and solutions already in place. Honestly, I can’t give a conclusive answer without more context, but I can offer five points of advice.
What is the state of the Python test solution?
How big and how bad is the existing Python test automation solution? Rewriting tests that already work fine has low return-on-investment. However, rewriting tests that have problems like flakiness or false positives might be worthwhile. More tests means more time, too. Please read my article, Our Test Automation Has Problems. Should We Start Over?, to learn what problems would warrant a rewrite.
Why not have two test solutions?
If the existing Python tests are fine, then rewriting them is a huge opportunity cost. Instead of rewriting existing tests, developers and testers could spend their time writing only the new tests in a new C# solution. The Python solution would be “legacy” and would not have any new tests added to it. Old tests would disappear with deprecated features, too. Eventually, the C# tests would take over. The main drawback for this possibility is the continued maintenance of a Python stack.
Do the manual testers have any programming experience?
Many manual testers do not have strong programming skills. Some may not have any programming skills at all! They will have a big learning curve when training to do test automation. Python would be a much easier language for them to learn than C# because it is concise, readable, and friendly for beginners. Conversely, Python would be fairly easy for C# developers to learn as they go.
What advantages will conformity bring?
Retraining workers and rewriting code is no small task. From a business perspective, they are investment costs. There must be significant returns that outweigh the cost of the transition. Make sure those returns are known and real.
Will developers also automate tests?
Many teams choose to write their test automation code in the same language as the product code so that developers can more easily automate tests. However, in my experience, developers typically don’t write many tests, especially when others on the team are dedicated testers. Test automation is difficult and has unique challenges. Some developers have bad attitudes about testing, too. Changing the language probably won’t change the deeper issues.
The decision to choose between C# and Python for test automation is very personal for me. I faced this choice directly when I started working at PrecisionLender. Even though I deeply love Python, we chose to use C#. It was the right choice: we were a Microsoft shop with no test solution (yet) and no Python stack in place. My team and I have no regrets.
There is nothing with test automation that either language can’t do. Both are solid choices. The best choice for a team depends more upon the team’s situation than differences between these languages.
When I was a kid, I was an enthusiastic Boy Scout. And every year, I looked forward to summer camp. For one full week, I would have a mini-adventure in the woods with my friends while earning new ranks and developing new skills. Summer camp was the highlight of every summer. As an adult, this is exactly how I feel about PyCon.
PyCon 2019 was my second time at PyCon. While I doubt any conference will ever have the same impact on me as my first PyCon, my second one was nevertheless every bit as good. I had a phenomenal experience. As always, I like to capture my reflections in an article so that I never forget the wonderful times I had. Here’s my story.
PyCon 2018 was a career-changing experience for me. I felt it at the time, and I can validate it now a year later. PyCon 2018 was my first serious engagement with the Python community. PyCon 2018 inspired me to speak at other conferences. PyCon 2018 introduced me to friends I still have today. As soon as PyCon 2018 ended, I knew that I needed to return for PyCon 2019.
Between 2018 and 2019, PrecisionLender (my employer) started doing much more Python work, especially in our data analytics division. I got approval from my manager to go to PyCon, but I also knew that others in the data division would benefit from PyCon as well. When I suggested the idea to the VP, he replied with one line: “Let’s do this thing!” With his blessing, I convinced four other PrecisionLender-ers to join me: Adam, Henry, Joe, and Raff.
I’m so thankful PrecisionLender approved our trips. Going with other friends from my company boosted not only my excitement for the conference but also my desire to learn new things. I’m proud to represent a company that supports its employees so well.
Good conferences are good but exhausting. They cram hundreds of adrenalized people into back-to-back activities requiring deep focus for hours at a time and for consecutive days. Amidst the mania, it is crucial to pace oneself. My friend Kojo sums this up perfectly in what he calls the “self care sprint.” It’s okay to step back to catch your breath. It’s vital to one’s mental health to take breaks, rest, and recover, especially at conferences as intense as PyCon.
Heeding Kojo’s advice, I took a #SelfCareSprint on the day before PyCon tutorials began. How so? I spent my afternoon at the Cleveland Museum of Art, which exhibits pieces from around the world dating from ancient times through the present day. Make no mistake: the Cleveland Museum of Art is world-class. In addition to their permanent collections, they had a special exhibit on Shinto artifacts from Japan. I barely had enough time to walk through all the galleries. What I did see impressed me, inspired me, and challenged me. Some pieces even spoke deeply to my soul.
The dichotomy of art and technology balance each other. Exploring pieces of art and the viewpoints they represent helped me center myself. I could clear my mind in preparation for the conference. I gained rest and recovery. I am human, after all.
PyCon 2019 hosted two days of tutorials before the main conference. Whereas talks are thirty minutes long and open to anyone, tutorials are three-hour sessions that require preregistration for limited seats. Tutorials are meant for hand-on learning with expert instructors. I had never attended tutorials at a conference before, and so this time, I wanted to try.
My first tutorial was Writing About Python (Even When You Hate Writing) by Thursday Bram. Since I do lots of blogging (and I ultimately want to write a book), I wanted to get first-hand advice on technical writing in the Python ecosystem. Thursday gave great advice on writing techniques and gotchas. The most valuable takeaway was her proofreading checklist. Her tutorial also inspired me to do something cool later in the conference. (Keep reading!)
My second tutorial was To trust or test? Automated testing of scientific projects with pytest. Unfortunately, this tutorial wasn’t right for me. I thought it would be about testing within data science, but it turned out to be a basic walkthrough of pytest. I didn’t learn any new material. What I did learn, though, was that I should be pickier with tutorials – I had to pay in advance, and I couldn’t just walk out to another talk.
My third tutorial was Escape from auto-manual testing with Hypothesis! by Zac Hatfield-Dodds. Hypothesis, a property-based testing tool, is hot right now. I first learned about it at the previous year’s PyCon, and I always wanted to learn more. Zac provided not only helpful lectures but a rigorous set of examples for us to complete. Hypothesis also works seamlessly with pytest. Zac made be a believer: Hypothesis is awesome! I need to spend more time learning it on my own.
As always, the talks were on point. I didn’t attend as many talks this year because I was too busy in the “hallway track,” but there were quite a few noteworthy ones that I attended.
In Don’t be a robot, build the bot, Mariatta showed how she and the Python core developers automated their GitHub workflow with the help of useful bots. It was cool to see how mundane processes can be automated away and how much more efficient teams can become.
In Break the Cycle: Three excellent Python tools to automate repetitive tasks, Thea Flowers showed how to use tox, nox, and Invoke to automate just about anything in Python. I’ll definitely refer back to this talk for testing.
In ¡Escuincla babosa!: Creating a telenovela script in three Python deep learning frameworks, Lorena Mesa showed us how serious machine learning can also be used for fun projects. Although the telenovela script she generated was short and humorous, it clearly proved that ML can get the job done.
In Scraping a Million Pokemon Battles: Distributed Systems By Example, Duy Nguyen showed how he scraped data from competitive Pokémon battles to level the playing field for new players. In the process, he developed a pretty slick distributed systems setup!
In Shipping your first Python package and automating future publishing, Chris Wilcox showed best practices on building and releasing Python packages. This talk was well-timed for me – I’ll definitely use this info for a current pet project of mine.
Dependency hell: a library author’s guide by Yanhui Li and Brian Quinlan will also be a great resource when considering dependencies for packages.
In to GIL or not to GIL: the Future of Multi-Core (C)Python, Eric Snow showed his thoughts for how to fix problems with the GIL and true multi-core processing.
In The Perils of Inheritance: Why We Should Prefer Composition, Ariel Ortiz made clear the nasty side effects inheritance can have and how composition is often a much better approach. The talk was fairly introductory, but I couldn’t agree more.
The expo hall was full of companies and organizations. The swankiest booths this year were:
Capital One – the Guido portrait and puzzle and the Zen of Python wall
Jetbrains – content developer tables for PyBites, Real Python, and others
Microsoft – four interactive Azure stations + active lab tables
However, my favorite company in the expo hall, hands down, was The Pokémon Company International. Their table was small and easily overlooked, but every time I passed by, it was packed. Everyone loves Pokémon! I got to meet a few of their engineers and managers. Apparently, they do much of their backend in Python. They’re also growing quite a lot. They were raffling off a giant Pikachu, and one of the engineers even developed a Google Home app that would make Pikachu respond whenever someone spoke to it! It was so charming to see them there. I’m glad that things are going well for Pokémon.
If you don’t overfill your swag bag, then you’re doing PyCon wrong. This year’s haul was as good as last year’s. I walked away with:
A deck of cards with the Zen of Python from Capital One
An artistic deck of playing cards from Heroku
16 packs of Pokémon cards
A JetBrains yo-yo
A few pairs of sunglasses
Water bottles from DoorDash, Wayfair, and Citadel
A guide to building Slack apps
The best t-shirt award goes to Microsoft for their Visual Studio Code shirt, with honorable mentions for LinkedIn and SmartBear. I also shared a good amount of this swag with my coworkers at PrecisionLender.
Cleveland (and greater Ohio) are renowned for craft breweries. Every time I return to Ohio, I’m always delighted by the beers I discover. I spent many lunches and dinners with a flight set on the side. Here’s where I went:
Hofbräuhaus Cleveland, twice! (I even bought the souvenir Maßkrug!)
Masthead Brewing Company
Noble Beast Brewing Company
Southern Tier Brewing Company
Great Lakes Brewing Company
The best was the Lichtenhainer from Noble Beast – a sour that tasted like a ham sandwich on sourdough. The worst was the “shampoo beer” from Southern Tier – did they forget to rinse the lines after cleaning them?
Back at PyCon 2018, I met an Aussie by the name of Julian Sequeira, co-founder of PyBites. We hit it off. In fact, meeting Julian is one of the reasons why I continue to engage the Python community today. Through Julian, I met other friends like Jason Wattier, Brian Okken, Cristian Medina, and many others. Leading up to PyCon 2019, Julian organized a BIG dinner at Great Lakes Brewing Company for a bunch of Python content developers: PyBites, Real Python, Python Bytes, Test & Code, tryexceptpass, and Automation Panda (me!). Not only was it a time of sweet reunion, but I finally got to meet others like Bob Belderbos, Michael Kennedy, and David Amos in person. One of the best parts of the dinner was when a few of us chose to walk back to the hotels over the bridge instead of calling taxis. The night was cold, but the experience was worth every second.
Sadly, I did not get to deliver a full talk or tutorial at PyCon 2019. Believe me, I submitted. But that didn’t stop me from trying – there’s always one more chance with lightning talks! One exercise during the Writing About Python tutorial was to pitch a lightning talk idea. At the time, I struggled to come up with a good topic. I first considered something about testing or being a tester, but those ideas just didn’t feel right. Then, I struck gold: what about giving helpful tips for blogging, based on my experiences with Automation Panda?
I put my idea on the call-for-lightning-talk-proposals on Saturday morning: “3 Quick Tips for Software Blogging.” When I didn’t receive any notification by lunchtime, I thought my pitch had been rejected. Then, while chilling in the quiet room at 3pm, I received an email: “Congrats! You’re giving your lightning talk today at 5pm!” Excitement, then panic, took over. I threw some slides together, rehearsed them in my head, and marched myself to the main auditorium. My lightning talk was second in queue, and I delivered it like a BOSS!
Ever since my first PyCon, I’ve dreamed about having a Python conference in the Carolinas. There was a PyCarolinas 2012 and a PyData Carolinas 2016, but both were one-hit wonders. My dream remained in my back pocket until PyCon 2019.
While meandering the expo hall on Friday, I ran into Tim Hopper and Brian Corbin, two friends who were also from the Carolinas. We talked about lots of things, but one point of discussion was about relaunching PyCarolinas. Later, Dustin Ingram, chair of PyTexas, tweeted that there would be a conference organizer’s open space on Saturday. I asked if I could join because of my PyCarolinas dreams, and he said absolutely yes. Brian and I both attended, made connections, and got tons of helpful information.
Dustin then asked me if I’d like to include a slide for PyCarolinas in the “regional conference parade” on Sunday morning after the lightning talks. Heck yeah! PyCarolinas was the very last slide as a call-to-action: We have a dream; come help us make it real!
At 10am on Sunday, I held an open space to talk about (re)launching PyCarolinas. 26 people came! We got everyone’s info, created a Slack room, and started throwing around ideas. In the week after the conference, over a hundred people signed up for our Slack room. The excitement is palpable. Our goal is to host PyCarolinas in summer of 2020 for 150+ people. I’m so thankful I got the opportunity to be the spark that lit this wildfire, on such a big stage.
Together with my blog, I use my Twitter handle @AutomationPanda for professional development. Twitter is especially helpful during conferences for communicating with friends and sharing experiences. During PyCon 2019, I crossed a big milestone: I hit over 1000 followers! That was cool.
I also made my first viral tweet, thanks to a sticker from Facebook:
If you read these reflections down this far, thank you. Seriously, I mean it.
The best part about PyCon 2019 for me was the time I spent with my friends.
PyCon 2019 was a high point for friendships. Everyone I knew was there. I couldn’t walk for 10 minutes around the convention center without running into someone I knew. I feel like I’m truly part of the Python community now. Here were just a few highlights:
Going there with my PL team: Adam, Henry, Joe, and Raff.
German dinner and souvenir Maßkrugs with Adam at Hofbräuhaus.
“Shampoo” beer with Joe and Adam at Southern Tier.
Snagging Pokémon cards on opening night with Mason Egger, and then running into Jason Wattier on the way.
Ramen dinner and Hilton rooftop drinks with the PL crew plus Mason.
Impromptu lunch with Adrienne so she could share the awesome things she’s accomplishing.