Students in my Python classes occasionally get the following error message: TypeError: object() takes no parameters This error message is technically true, as I’ll explain in a moment. But it’s surprising and confusing for people who are new to Python, because it doesn’t point to the source of the actual ...

Let’s define a simple Python function: In [1]: def foo(x): ...: return x * x ...: In [2]: foo(5) Out[2]: 25 In [3]: foo(10) Out[3]: 100 As we can see, this function has a single parameter, “x”.  In Python, parameters are local variables whose values are set by whoever is ...

The most common question I get from students in my Python classes is: How can we practice and improve our skills after the course is over? These students realize that no matter how good a course might be, they won’t retain very much if they don’t use and practice their ...

Python’s “subprocess” module makes it really easy to invoke an external program and grab its output. For example, you can say import subprocess print(subprocess.check_output('ls')) and the output is then $ ./blog.py b'blog.py\nblog.py~\ndictslice.py\ndictslice.py~\nhexnums.txt\nnums.txt\npeanut-butter.jpg\nregexp\nshowfile.py\nsieve.py\ntest.py\ntestintern.py\n' subprocess.check_output returns a bytestring with the filenames on my desktop. To deal with them in a more serious ...

One of Python’s mantras is “batteries included.” which means that even with a bare-bones installation, you can do quite a bit. You can (and should) install packages from PyPI, but many day-to-day tasks can be accomplished with just the built-in data structures, functions, and methods. What I’ve discovered over the ...