reusability.qmd

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filters:
  - pyodide
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# Reusability

{{< video https://youtu.be/sPpbyXyRlQI >}}

Let’s look at an example.  Here’s a file I created called Penchord_Wizardry.py.

```{python}

import random

# Class defining a Penchordian
class Penchordian :
    def __init__(self, name):
        self.name = name
        self.is_a_wizard = False

    def write_model(self, type_of_model):
        print (f"{self.name} is now writing a {type_of_model} model.")

    def tell_joke(self, prob_success):
        if random.uniform(0,1) < prob_success:
            print (f"{self.name} attempted a joke.  People loved it!")
        else:
            print (f"{self.name} attempted a joke.  It fell flat.")

# Function to turn someone into a wizard
# Input subject must be an object with a "name" string attribute and a
# "is_a_wizard" boolean attribute
def turn_into_a_wizard(subject):
    subject.is_a_wizard = True
    print (f"{subject.name} is now a wizard.")

```


Then I'm going to create a new file in the **same folder** as `Penchord_Wizardry.py`.

:::{.callout-tip}
It is possible to call in functions from a Python file stored in a different folder or subfolder - but it starts getting quite complicated to navigate to them in the code, so we won't cover that today.
:::

At the beginning of my new file I'm going to `import Penchord_Wizardry` to get access to the functions from `Penchord_Wizardry.py`.

```{python}
# import the entire Penchord_Wizardry module (the Penchordian class and the
# turn_into_a_wizard function)
import Penchord_Wizardry

import random

list_of_penchordian_names = ["Dan", "Sammi", "Kerry", "Mike", "Anna", "Tom",
                             "Amy C", "Amy H", "Chrissie"]

# Randomly select three PenCHORDian names
# random.sample selects three elements from a list without replacement
# (if you want values to be able to be repicked (replacement), use
# random.choices)
chosen_penchordian_names = random.sample(list_of_penchordian_names, 3)

list_of_penchordians = []

# Create some Penchordian objects using the definition from the imported
# module
for name in chosen_penchordian_names:
    list_of_penchordians.append(Penchord_Wizardry.Penchordian(name))

# Call a couple of the class methods on the three created Penchordian objects
for penchordian in list_of_penchordians:
    penchordian.write_model("Discrete Event Simulation")
    penchordian.tell_joke(0.1)


```



I can also choose just to import the bit(s) of the module I need, rather than the whole thing.

Here we don't import the class `Penchordian`, but we do import the function `turn_into_a_wizard`.

:::{.callout-tip}
Note that because we've imported the specific function by name, we can just then use `turn_into_a_wizard`.
:::


```{python}
# just import the turn_into_a_wizard function
from Penchord_Wizardry import turn_into_a_wizard

# Define a new class called HSMA, which has two attributes - a name, and an
# is_a_wizard boolean
class HSMA:
    def __init__(self, name):
        self.name = name
        self.is_a_wizard = False

# Create a new HSMA object, whose name is Gandalf
my_promising_HSMA = HSMA("Gandalf")

# Turn Gandalf into a wizard using the function we imported from the
# Penchord_Wizardry module
turn_into_a_wizard(my_promising_HSMA)
```

In comparison, if we imported the whole module instead, our code would look like this:

```{python}
# just import the turn_into_a_wizard function
import Penchord_Wizardry

# Define a new class called HSMA, which has two attributes - a name, and an
# is_a_wizard boolean
class HSMA:
    def __init__(self, name):
        self.name = name
        self.is_a_wizard = False

# Create a new HSMA object, whose name is Gandalf
my_promising_HSMA = HSMA("Gandalf")

# Turn Gandalf into a wizard using the function we imported from the
# Penchord_Wizardry module
Penchord_Wizardry.turn_into_a_wizard(my_promising_HSMA)
```