Exercises in .NET with Andras Nemes

Python language basics 23: using the global __name__ attribute

Introduction

In the previous post we saw one way to break up the number guessing game into short functions. We saw examples of void methods and functions with and without parameters. We also said that there are usually several possible ways to organise the code into functions.

However, we also saw that calling the number guessing game from the command line didn’t execute anything. Python has no way of knowing what you want to do with the code, it only sees a collection of functions.

The solution is easy but we need to learn a new language construct first.

Double-underscore variables

Python has a small number of built-in variables surrounded by double underscores ‘__’. These are populated by Python during code execution, i.e. the Python runtime, and can be accessed in code if you need them.

One such variable is…

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Python language basics 22: organising code into functions

Introduction

In the previous post we looked at functions which are one of the most important building blocks of any serious programming language. We saw how to use the ‘def’ keyword to define a function. We also discussed the difference between void functions – methods – and functions that have a return value.

In this post we’ll organise our previous number guessing game into functions as an exercise.

Note that there’s most often no single solution when you break up your code into functions. The one presented here is only one solution out of many.

Starting point

As a reminder here’s the number guessing game code:

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Python language basics 21: functions in Python

Introduction

In the previous post we took a break from going through the Python language features and looked at how to execute a Python source file from the Windows command prompt. We saw how easy it was to execute a file without having to go through any steps before such as code compilation like in Java with the “javac” tool.

In this post we’ll return to Python language constructs and see how functions are built.

Functions and methods

Functions are reusable code blocks that execute the code within the function body.

Consider the following code:

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Python language basics 20: running a Python file from the command line

Introduction

In the previous post we looked at how for-loops are constructed in Python using the range function. They are in fact practically the same as foreach-loops as we iterate through a range of integers and we perform something with each integer. However, that is the closes approximation of the more traditional integer-based for-loops of other programming languages like Java:

for (int i = 0; i < 10; i++)
{
}

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