it-ebooks - Full Speed Python

v0.4.3

Joo Ventura

This book aims to teach the Python programming language using a practical approach. Its method is quite simple: after a short introduction to each topic, the reader is invited to learn more by solving the proposed exercises.

These exercises have been used extensively in my web development and distributed computing classes at the Superior School of Technology of Setbal. With these exercises, most students are up to speed with Python in less than a month. In fact, students of the distributed computing course, taught in the second year of the software engineering degree, become familiar with Pythons syntax in two weeks and are able to implement a distributed client-server application with sockets in the third week.

Please note that this book is a work in progress and, as such, may contain a few spelling errors that may be corrected in the future. However it is made available now as it is so it can be useful to anyone who wants to use it. I sincerely hope you can get something good through it.

The source of this book is available on github (https://github.com/joaoventura/full-speed-python). I welcome any pull requests to correct misspellings, suggest new exercises or to provide clarification of the current content.

All the best,

Joo Ventura - Adjunct Professor at the Escola Superior de Tecnologia de Setbal.

In this chapter we will install and run the Python interpreter in your local computer.

1. Download the latest Python 3 release for Windows on https://www.python.org/downloads/windows/ and execute the installer. At the time of writing, this is Python 3.6.4.

2. Make sure that the Install launcher for all users and Add Python to PATH settings are selected and choose Customize installation.

   Windows installation

3. In the next screen Optional Features, you can install everything, but it is essential to install pip and pylauncher (for all users). Pip is the Python package manager that allows you to install several Python packages and libraries.

4. In the Advanced Options, make sure that you select Add Python to environment variables. Also, I suggest that you change the install location to something like C:\Python36\ as it will be easier for you to find the Python installation if something goes wrong.

   Windows installation

5. Finally, allow Python to use more than 260 characters on the file system by selecting Disable path length limit and close the installation dialog.

   Windows installation

6. Now, open the command line (cmd) and execute python or python3. If everything was correctly installed, you should see the Python REPL. The REPL (from Read, Evaluate, Print and Loop) is a environment that you can use to program small snippets of Python code. Run exit() to leave the REPL.

   Python REPL

You can download the latest macOS binary releases from https://www.python.org/downloads/mac-osx/. Make sure you download the latest Python 3 release (3.6.4 at the time of writing). You can also use Homebrew, a package manager for macOS (https://brew.sh/). To install the latest Python 3 release with Homebrew, just do brew install python3 on your terminal. Another option is to use the MacPorts package manager (https://www.macports.org/) and command port install python36.

Finally, open the terminal, execute python3 and you should see the Python REPL as above. Press Ctrl+D or write exit() to leave the REPL.

To install Python on Linux, you can download the latest Python 3 source releases from https://www.python.org/downloads/source/ or use your package manager (apt-get, aptitude, synaptic and others) to install it. To make sure you have Python 3 installed on your system, run python3 --version in your terminal.

Finally, open the terminal, execute python3 and you should see the Python REPL as in the following image. Press Ctrl+D or write exit() to leave the REPL.

In this chapter we will work with the most basic datatypes, numbers and strings. Start your Python REPL and write the following:

Basically, you are declaring two variables (named a and b) which will hold some numbers: variable a is an integer number while variable b is a real number. We can now use our variables or any other numbers to do some calculations:

Python also has support for string datatypes. Strings are sequences of characters (like words) and can be defined using single or double quotes:

You can add strings to concatenate them but you can not mix different datatypes, such as strings and integers.

However, multiplication works as repetition:

1. Try the following mathematical calculations and guess what is happening: ((3 / 2)), ((3 // 2)), ((3 % 2)), ((3**2)).

   Suggestion: check the Python library reference at https://docs.python.org/3/library/stdtypes.html#numeric-types-int-float-complex.

2. Calculate the average of the following sequences of numbers: (2, 4), (4, 8, 9), (12, 14/6, 15)

3. The volume of a sphere is given by (4/3 * pi * r^3). Calculate the volume of a sphere of radius 5. Suggestion: create a variable named pi with the value of 3.1415.

4. Use the modulo operator (%) to check which of the following numbers is even or odd: (1, 5, 20, 60/7).

   Suggestion: the remainder of (x/2) is always zero when (x) is even.

5. Find some values for (x) and (y) such that (x < 1/3 < y) returns True on the Python REPL. Suggestion: try (0 < 1/3 < 1) on the REPL.

Using the Python documentation on strings (https://docs.python.org/3/library/stdtypes.html?#text-sequence-type-str), solve the following exercises:

1. Initialize the string abc on a variable named s:

   1. Use a function to get the length of the string.