Python quine

This post is a few years old now, so some details or my opinions might be out of date.

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Python quine

A quine is a program that provides its own source code as output. It's one of the first programs I'll try and write when learning a new language, but it wasn't always obvious to me how. At first these cute programs seemed like an almost impossible esoteric IOCCC -tier artform crafted by programming artisans. I want to share the general concepts used to construct programs like these and explore some of the things that can be done with them. We can access most of the source code already with this function by reading expr. This string data is actually used twice in the output string! Once at the start of the output, and again as part of the source of the expression. This reuse of information is a common trick when writing quines. JavaScript allows this kind of introspection for arbitrary functions by just converting them to strings:. This is very similar to our pseudocode example, except we use a function rather than a generic expression. More boilerplate is required to glimpse behind the curtain and grab the code, but it uses the exact same approach at the previous examples. While these quines are easy to make and understand, the functionality to achieve them isn't common to most programming languages they're also a bit dubious.

The second half of the output is the python quine as the first, it repeats, so we can simplify our template a lot.

A quine program , or quine , is a program that outputs its own source code when run. Instead, it must compute its own source code. The trick is getting the string just right. How you do this varies from language to language depending on how variables are declared, the method of interpolation, the possible need for semicolons and newlines, the kinds of quotes required, and so on. Dealing with quotes is interesting; you need to find a way to specify that a quote character is to be printed without actually using a quote character. Note : In each of the following examples, the programs are assumed to have no newline at the end of the program text unless specified.

A quine is a computer program that takes no input and produces a copy of its own source code as its only output. The standard terms for these programs in the computability theory and computer science literature are "self-replicating programs", "self-reproducing programs", and "self-copying programs". A quine is a fixed point of an execution environment, when that environment is viewed as a function transforming programs into their outputs. Quines are possible in any Turing-complete programming language, as a direct consequence of Kleene's recursion theorem. For amusement, programmers sometimes attempt to develop the shortest possible quine in any given programming language. The idea of self-reproducing automata came from the dawn of computing, if not before. John von Neumann theorized about them in the s. In general, the method used to create a quine in any programming language is to have, within the program, two pieces: a code used to do the actual printing and b data that represents the textual form of the code. The code functions by using the data to print the code which makes sense since the data represents the textual form of the code , but it also uses the data, processed in a simple way, to print the textual representation of the data itself.

Python quine

So, first things first:. Roughly speaking, a quine is a self-reproducing program: if you run it, it generates itself. Devising the shortest possible quine in some given programming language is a common hackish amusement. The program is self-reproducing because the output of the program is the program itself.

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Python Visualizing O n using Python. We have to use single quotes here, otherwise the variables will automatically get interpolated. Last commit date. Retrieved 20 April These expression based quines can be run in a REPL. How you do this varies from language to language depending on how variables are declared, the method of interpolation, the possible need for semicolons and newlines, the kinds of quotes required, and so on. Continuing with the data transform idea, we can also just encode the whole string. You should learn to write them. If you use puts instead of print then you will need a newline at the end of your source code file. Of course, to get away with as much as possible, while making the code legal although nasty , we can just declare printf ourselves and omit the return 0. It was interesting to see the author work through the major obstacles one by one when writing a quine. A polyglot program is not required to have a self-reproducing quality, although a polyglot program can also be a quine in one or more of its possible ways to execute. Save Article.

Hey everyone, this is an interesting tutorial about quine in Python. Quine is a program that does not take any input and outputs its own source code.

So it reruns the same file as JavaScript which renders the quine to the the page, replacing the original content. The version that appears in several places on the web, including the Rosetta Code quine page, is a little different: it doesn't even write to standard output. If you're going to cheat, the best approach is probably this one. These quines can be easily found with some iterative copying in a shell or some other REPL:. I want to share the general concepts used to construct programs like these and explore some of the things that can be done with them. This is very similar to our pseudocode example, except we use a function rather than a generic expression. Python Merge Python key values to list. The shortest possible quine in python is just a single line of code! The source code contains a string array of itself, which is output twice, once inside quotation marks. At first these cute programs seemed like an almost impossible esoteric IOCCC -tier artform crafted by programming artisans. Retrieved June 14,