I have worked with hundreds of developers in my career, but i have met only a few professionals so far. A lot of people think professionalism is having a high level of technical knowledge, years of experience and creating complex stuff that common folks can't create, but that is not even close to the definition of professionalism.
What is professionalism?
Professionalism is primarily a soft skill. It is a mindset, and an attitude towards work. Professionalism is finishing stuff on time and with quality. Professionalism is showing up and doing your work when it's the hardest. Professionalism is accepting your career as an important life priority. Professionalism is choosing the hardest task for the project benefit.. and many other things.
As you see, there is no technical knowledge and experience involved, it is an attitude.
Here is a nice quote from a masterpiece by Steven Pressfield called "The War of Art" about turning professional:
"Turning PRO is a mindset. If we are struggling with fear, self-sabotage, procrastination, self-doubt, etc., the problem is we're thinking like amateurs. Amateurs don't show up. Amateurs crap out. Amateurs let adversity defeat them. The pro thinks differently. He shows up, he does his work, he keeps on truckin', no matter what" - Steven Pressfield
Professionalism is rarely a topic of software books and blogs, but i have come accross a pretty nice chapter about professionalism in a book called Soft Skills by John Somnez (a.k.a. The Simple Programmer).
Here is a short excerpt from that chapter:
"Simply put, a professional is someone who takes their responsibilities and career seriously and is willing to make the tough choices that have to be made - often at their own expense - for the purpose of doing what they know is right. A professional is someone you can count on to get a job done and do it right. Perhaps most importantly, a professional is consistent - stable. A professional has high-quality standard for their work and you can expect a professional to adhere to it each and every day. When a professional doesn't show up, you better call emergency dispatch, because there is certainly something wrong" - John Somnez
John is right, but unfortunately professionals are almost extinct in modern software development. That explains so many emergency calls.