Collatz Conjecture

2016-09-03, post № 140

mathematics, programming, Pygame, Python, #3n+1, #three n plus one

The Collatz conjecture states that every positive integer 𝑘 > 𝟢 will — if you iteratively set 𝑘 to 𝑓 (𝑘) — result in 𝟣 (function shown beneath).
The graph beneath shows the path length of numbers from 𝟣 to 𝟣𝟢 𝟢𝟢𝟢. In this range, 𝟨 𝟣𝟩𝟢 is the number with the most steps, 𝟤𝟨𝟣.

f(k)={\begin{cases}\frac{k}{2}&{\text{if }}k\mod 2=0\\3\cdot k+1&{\text{if }}k\mod 2=1\end{cases}}
Source code: collatz-conjecture.py

Curses Cam

2016-08-27, post № 139

curses, programming, Pygame, Python, #camera, #color depth, #low resolution, #shell image, #.si, #text-based images

Normally a shell lets you input via a text command and outputs via a text message [1]. When using curses you can extend its capabilities and program for example games with limited graphics.
I wanted to go even further and built a Python script that — using Pygame’s camera module and curses — captures an image from an attached webcam (USB or built-in), transforms it and displays it on the shell.
Although both the resolution and the color depth are shrunk immensely, the resulting colored text on the shell often resembles the scene caught and has a nice visual effect.
There are two modes, camera and file viewer, which can be toggled by pressing ‘F1’. In camera mode you can see what the camera is seeing and snap a photo, which then will be saved to disk. In file viewer mode you can view the photos you took. The files will be saved in an out/ directory located in the current Python file’s directory. Saved photos have the file extension .si (“shell image”).
Unfortunately, Pygame’s camera module does neither work on Mac OS X nor on Windows. Thus this program is only properly usable under Linux [2] systems. You obviously also need a webcam or else you will not be able to take a picture.


  • ‘F1’ switches between camera and file viewer mode,
  • ‘Space’ saves the current photo as a .si file (only in camera mode),
  • Left or down arrow key decreases current file’s id (only in file viewer mode),
  • Right or up arrow key increases current file’s id (only in file viewer mode).
Source code: curses-cam.py

Jetris CE

2016-08-20, post № 138

curses, games, programming, Python, #bag, #bag method, #Tetris

This game’s challenge is
to arrange the falling blocks.
Stay alive forever.

Jetris Console Edition is my second Tetris clone (see Jetris for the first one). It is programmed in Python and uses the curses module to display all its graphics on the shell.
Despite it running purely on the shell, I managed to eliminate any noticeable graphics update bugs. Furthermore the code to clear lines differs immensely from Jetris and actually works properly.
To enhance gameplay I implemented the so-called bag method. Instead of choosing pieces at random, a bag gets filled with all seven possible pieces. Each time you get a new piece, that piece gets randomly chosen out of the bag. If the bag is empty, it gets refilled. That way it is ensured that there will be no more than twelve pieces between two identical pieces (worst-case scenario). Also there will no more than four ‘S’ or ‘Z’ pieces in a row which makes the game fairer.
The pieces initially fall at one pps (pixel per second) and the game runs at twelve tps (ticks per seconds). Every ten cleared lines the speed increases by one tick or one twelfth of a second until it stays at the minimum speed, one twelfth of a second. [1]
The game’s clock is handled by a thread and graphics updates are made when they are needed (there are no fps).
To achieve the pieces blocky look I used two spaces and a color pair whose background color is the piece’s color. On the shell two fully filled characters look like a square.
You also have the option to change your key bindings — which get saved on disk —, pause the game and there is a high score list — which also gets saved on disk. The files are located where the Python code file resides.

Source code: jetris-ce.py
Jonathan Frech's blog; built 2021/04/16 20:21:20 CEST