Don't Repeat Yourself
An important concept in programming is not to write the same piece of code twice. What does that mean and what to do instead?
Welcome interesed student of the LiFi-project. I am glad you want to jump ahead, but I am still building this course as we move through the semester, and this part is not ready yet. Please come back later.
Don't Repeat Yourself!
An important principle in programming is "Don't Repeat Yourself". Code that we need in several places of our program should be given a name and wrapped in a function. We saw how to do this earlier in this section. We can simply call functions like any other command from anywhere in our program.
Modules
If we put all our custom created, useful functions into a file and call it, for example, useful_funcs.py ,we have created a so-called module.
The great benefit of modules is that we can reuse and import them in different programs. These can be our programs or the program's from someone else. The latter requires that person to have a copy of our module:
Libraries
If you program for a longer time, you might at some point have written so many functions that it makes sense you create separate modules for them. You now have a set of Python-files, each containing functions that address a common problem or belong together in some other way. If in turn those modules somehow belong together because they too address a common, but larger issue, you can bundle those modules into a so-called library. Look at the example below, where the three modules geometry.py, algebra.py, and arithemtic.py each contain functions to solve specific problems from a particular domain. However, the modules share that they all solve mathematical problems. It therefore makes sense to group them into a library called Math.
So, here is the difference between a module and a library: a module is a collection of functions that live in one Python-file. A library is a collection of related modules bundled together. So in that sense, a library is bigger than a module.
GitHub and PyPI
When we're happy with our library, we can share it with the world. There are different options for that, but the online-platform GitHub is a great place to start. On GitHub, we can publish code and others can get inspired or re-use that code in their projects. The code examples for this course live on GitHub, too:
Another way for everyone to use your library is to have it listed in the Python Package Index (PyPI), which allows to download and install your library with one line on the command line:
pip install my_libraryAfter this command ran successfully, one can import functions from the library in their programs like this:
from my_library import calc_CFrom now on, the function calc_C can be used in that program like any other function.
It is important to note that a library can contain not just functions, but is often used to declare constant values, too. This is, in fact, a use case in our LiFi-project.
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