algs4-py

algs4-py is a Python 3 port of the Java code in Algorithms, 4th Edition.

Target audience

algs4-py is intended for instructors and students who wish to follow the textbook Algorithms, 4th Edition by Sedgewick and Wayne. It was first created in 2018 by teaching assistants and instructors at ITU Copenhagen, where the introductory course on Algorithms and Data Structures is taught bilingually in Java and Python 3.

Installation

This library requires a functioning Python 3 environment, for example the one provided by Anaconda. Some optional visual and auditory features depend on the numpy and pygame packages.

With pip and git

If git is available, the following command will install the library in your python environment:

pip install git+https://github.itu.dk/algorithms/AlgorithmsInPython

When requested, you will need to enter your ITU credentials.

With pip and zip

To install this library without git:

1. Download and unzip the repository.
2. Open a command prompt or terminal and navigate to the downloaded folder. There should be the file setup.py.
3. Use the command pip3 install . to install the package (this will also work for updating the package, when a newer version is available). If your python installation is system-wide, use sudo pip3 install .

Step-by-step guide for Windows

To install the python package algs4:

• Download the repository by pressing the green "Clone or download" button, and pressing "Download ZIP".
• Extract the content of the zip to your Desktop (you can delete the folder after installing the package).
• Open the "Command Prompt" by pressing "Windows + R", type "cmd" in the window that appears, and press "OK".
• If you saved the folder on the Desktop you should be able to navigate to the folder by typing "cd Desktop\AlgorithmsInPython-master".

C:\Users\user>cd Desktop\AlgorithmsInPython-master

• When in the correct folder, type pip install . to install the package.

C:\Users\user\Desktop\AlgorithmsInPython-master>pip install .

• After this, the package should be installed correctly and you can delete the folder from your Desktop.

Test the installation

To test that the package is installed correctly, run python in interactive mode and enter import algs4.

user@host:~$ python 
Python 3.7.6 | packaged by conda-forge | (default, Jan  7 2020, 22:33:48) 
[GCC 7.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import algs4
>>> 

If no error message appears, the library has been installed correctly.

Usage

The python package algs4 has a hierarchical structure with seven sub-packages:

• algs4.fundamentals
• algs4.sorting
• algs4.searching
• algs4.graphs
• algs4.strings
• algs4.stdlib
• algs4.errors

The first five packages correspond to the first five chapters of Algorithms, 4th Edition. The stdlib package is based on the one from the related book Introduction to Programming in Python. The package errors contains some exception classes.

All filenames and package names have been written in lower_case style with underscores instead of the CamelCase style of the Java version. For example EdgeWeightedDigraph.java has been renamed to edge_weighted_digraph.py. Class names still use CamelCase though, which is consistent with naming conventions in Python.

Example

A simple program, stored as a file hello_world.py, looks like this:

import algs4.stdlib.stdio

algs4.stdlib.stdio.write("Hello World!\n")

It can be run with the command python hello_world.py.

You can import classes, such as the class EdgeWeightedDigraph, with

from algs4.graphs.edge_weighted_digraph import EdgeWeightedDigraph

Some files contain multiple classes, for example:

from algs4.fundamentals.uf import UF
from algs4.fundamentals.uf import QuickUnionUF

Look into the examples directory for further examples.

Documentation

You can use python's built-in help function on any package, sub-package, public class, or function to get a description of what it contains or does. This documentation should also show up in your IDE of choice. For example help(algs4) yields the following:

Help on package algs4:

NAME
    algs4

PACKAGE CONTENTS
    errors (package)
    fundamentals (package)
    graphs (package)
    searching (package)
    sorting (package)
    stdlib (package)
    strings (package)

FILE
    (built-in)

Development

algs4-py has known bugs and has not been tested systematically. We are open to pull requests, in particular, we appreciate the contribution of high-quality test cases, bug-fixes, and coding style improvements. For more information, see the CONTRIBUTING.md file.

Contributors

• Andreas Holck Høeg-Petersen
• Anton Mølbjerg Eskildsen
• Frederik Haagensen
• Holger Dell
• Martino Secchi
• Morten Keller Grøftehauge
• Morten Tychsen Clausen
• Nina Mesing Stausholm Nielsen
• Otto Stadel Clausen
• Riko Jacob
• Thore Husfeldt
• Viktor Shamal Andersen

License

This project is licensed under the GPLv3 License - see the LICENSE file for details

Links to other projects

• algs4 is the original Java implementation by Sedgewick and Wayne.
• The textbook Introduction to Programming in Python by Sedgewick, Wayne, and Dondero has a somewhat different approach from Algorithms, 4th Edition, and is therefore not suitable for a bilingual course. Nevertheless, our code in algs4/stdlib/ is largely based on the source code associated with that book.
• pyalgs is a Python port of algs4 that uses a more idiomatic Python coding style. In contrast, our port tries to stay as close to the original as possible, so that it can be used with less friction in a bilingual course.
• Scala-Algorithms is a Scala port of algs4.
• Algs4Net is a .NET port of algs4.