Intermediate Programming with Python: Glossary

Python scripts are plain text files, usually with the .py extension.

You execute Python scripts at the command-line with the Python interpreter.

Values are displayed using the print function.

Comments are indicated with #. Anything between the # and the end of the line is ignored.

Most programs will require ‘Loops’ and ‘Branching’ constructs.

while statements, in addition to for, allow for looping through sections of code

The programmer must provide a condition to end a while loop.

The official Python documentation is a good reference to the core Python language.

You should ensure that the correct Python version is selected in the online documentation, as language features have changed over time.

There are several ways to check the Python version you are using.

The help() function displays the documentation for a given Python object.

In Jupyter Notebooks, the ? command will display the same result as help() in a separate panel, with formatted text.

The type() function returns the type of a Python object.

Illegal language constructs are called syntax errors. They are detected by the Python parser.

Legal code can also produce errors during execution, known as run-time errors.

In Python, run-time errors raise exceptions.

Exceptions are handled with the try-catch language feature.

You can raise your own exceptions with the raise keyword.

Look Before You Leap (LBYL) is a defensive programming style where you check for problems before executing important code.

It’s Easier to Ask Forgiveness than Permission (EAFP) is a programming style where you wait for errors to occur and then handle them later.

Files are opened with the open() function.

The open() function returns a file object.

Files need to be closed when they are no longer required by your program.

The close() method of the file object closes a file.

The with statement provides an elegant and safe way to automatically close your files.

Data can be read from text files a line at a time by the readline() file object method.

If you want to process each line of a text file in order, then iteration is useful.

Data can be written to a file with the write() file object method.

Patterns are common and repeatable recipes for common problems. The text file sequential processing pattern is simple, robust and efficient.

Don’t repeat yourself. Keep your code DRY by using functions.

Break programs down into functions to make them easier to understand.

Define a function using def with a name, parameters, and a block of code.

Defining a function does not run it.

Arguments in the function call are matched to the parameters in the function definition.

Optional arguments have a default value in the function definition.

Functions return results with the return statement.

Use docstrings to document your functions in a standard way.

Using command-line arguments can make your programs easier to use and reuse.

Modules are simply Python files.

To use code from a module, it has to be imported.

The import command is used to import code from a module.

There are different ways to import from a module. Select the appropriate method based on the required effect.

__name__ is a string containing the module name.

For files directly executed by Python, __name__ gets the special value “main”, indicating that this is the main file.

The if __name__ == "__main__" expression prevents code from running when the module is being imported.

Verification vs validation, different levels.

There are numerous frameworks and tools, but we use pytest here.

Test Driven Development places the focus on writing just enough code at each point in time to make a failing test pass.

A doctest consists of a multi-line string containing a mixture of text, code and expected results (implicit assertions).

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