From 6c65fe715655aecacc575ebbae167230fb7d48fa Mon Sep 17 00:00:00 2001 From: waldek Date: Fri, 29 Oct 2021 12:08:01 +0200 Subject: [PATCH] adds functions --- learning_python3.md | 143 +++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 140 insertions(+), 3 deletions(-) diff --git a/learning_python3.md b/learning_python3.md index 448d91d..e692174 100644 --- a/learning_python3.md +++ b/learning_python3.md @@ -307,6 +307,8 @@ else: print("you are at a dangerous crossroad in life!") ``` +⛑ **Do not fight the automatic indentation in your IDE! Pycharm is intelligent enough to know when to indent so if it does not indent by itself, you probably made a syntax error.** + ## Class string methods Let's take the logic above and implement it in a real program. @@ -423,10 +425,12 @@ else: We can use conditional logic to create quite elaborate decision processes. Let's build a mini text based adventure game. Granted it's not a *tripple A* game but it will train your `if` and `else` skills plus it will highlight some issues we'll overcome in the next section. -Consider the diagram below. ![adventure game](./assets/text_based_adventure_game.png) +Consider the diagram above we can imagine a program that functions nicely with the code below. +It is not very *readable* nor *scalable*. + ```python3 answer = input("You're at a cross section. Do you go left or right?") if answer.startswith("l"): @@ -475,12 +479,108 @@ else: exit(0) ``` +I urge you to read up on some [best practices](https://www.tutorialdocs.com/article/python-conditional-statements-tips.html) for `if` statements. +We will not improve on this particular example but I do advise you to create a similar style game during one of the workshops once we have learned some new tricks. + # Creating your own functions +One of the *issues* we have in the text based game example is duplicate code. +At two spots we execute almost identical code and this is something that should be avoided at all costs! +Why write the same thing over and over? +You're better off writing it **once** and use it **lots**. +This is where **functions** come into play. + +Python ships with a lot of built-in functions but we can create our own very easily. +The keyword to define a function in python is `def`. +All the code that is *indented* will be executed when we **call** the function. +Here is a basic abstraction of correct syntax. + +```python3 +def first_function(): + print("I'm a function") + print("Hear me roar!") +``` + +If you type *only* the code above in a new script, and run it, you won't see much. +This is because you only **created** the function. +To use it you need to **call** it. +This is done as follows. + +```python3 +def first_function(): + print("I'm a function") + print("Hear me roar!") + +first_function() +``` + +Learning how to create functions is a big step in your programming journey. +It can seem confusing at first because the code execution *appears* to jump around. +This is however **not** the case. +Your script is still read and executed **line by line** so you can not call a function **before** you defined it! +For now you should not overthink the structure of you scripts. +As long as they work you should be happy. +We'll dive into the proper *anatomy* of a program real soon. + ## Functions that *do* something -TODO recipe with variable flavor (chocolate, vanilla, ...) -TODO pretty_print +The first function I showed you above performs a series of actions each time it is called. +We can use it to *bake cakes* for example. +Below we create **one** function to bake the cake, and call it **three** times to bake three cakes. + +```python3 +def bake_chocolate_cake(): + print("mix the base ingredients") + print("add the chocolate flavour") + print("put in the oven") + print("enjoy!") + +bake_chocolate_cake() +bake_chocolate_cake() +bake_chocolate_cake() +``` + +Now, you might like a *vanilla* cake from time to time. +Easy, we'll just write a second function for that purpose. + +```python3 +def bake_chocolate_cake(): + print("mix the base ingredients") + print("add the chocolate flavour") + print("put in the oven") + print("enjoy!") + +def bake_vanilla_cake(): + print("mix the base ingredients") + print("add the vanilla flavour") + print("put in the oven") + print("enjoy!") + +bake_chocolate_cake() +bake_chocolate_cake() +bake_vanilla_cake() +bake_chocolate_cake() +bake_vanilla_cake() +``` + +Voila, we can now make as many chocolate and vanilla cakes as we want! +But what about *bananas*? +Following our logic we can create a *third* function to bake a banana cake but you're probably seeing a *pattern* here. +Each `bake_FLAVOR_cake` function is almost identical, just for the flavoring. +We can create one generic `bake_cake` function and just add the custom flavor each time we actually *bake* a cake. +This is done with arguments. + +```python3 +def bake_cake(flavor): + print("mix the base ingredients") + print("add the {} flavor".format(flavor)) + print("put in the oven") + print("enjoy!") + +bake_cake("chocolate") +bake_cake("vanilla") +bake_cake("banana") +``` ## Variable scope @@ -488,6 +588,43 @@ TODO pretty_print TODO basic math functions +## Some links to read up on + +* some [best practices](https://able.bio/rhett/python-functions-and-best-practices--78aclaa) for functions +* more details on [variable scope](https://pythongeeks.org/python-variable-scope/) + +# Coding challenge - Pretty Print + +Can you write me a function that decorates a name or message with a *pretty* character. +Kind of like the two examples below. + +``` +########## +# Wouter # +########## + +################# +# Python rules! # +################# +``` + +
+ Spoiler warning + +```python3 +def pretty_print(msg, decorator="#"): + line_len = len(msg) + (len(decorator) * 2) + 2 + print(decorator * line_len) + print("{} {} {}".format(decorator, msg, decorator)) + print(decorator * line_len) + +pretty_print("Wouter") +pretty_print("Python rules!") +pretty_print("Alice", "-") +``` + +
+ # Using the standard library TODO import random exercise (digital dice)