# Syntax Guide¶

Warning

This extension currently works best when paired with the following themes:

When using other themes (such as alabaster) the icons for the exercise and solution admonitions are missing on the top left. We would like to make this more theme agnostic and status can be found in this issue

Note

To use this extension in a Jupyter Book project, add sphinx_exercise as an extension in the _config.yml file.

sphinx:
extra_extensions:
- sphinx_exercise


Note

This documentation utilized the Markedly Structured Text (MyST) syntax.

## Exercise Directive¶

An exercise directive can be included using the exercise pattern. The directive is enumerated by default and can take in an optional title argument. The following options are also supported:

• label : text

A unique identifier for your exercise that you can use to reference it with {ref} and {numref}. Cannot contain spaces or special characters.

• class : text

Value of the exercise’s class attribute which can be used to add custom CSS or JavaScript.

• nonumber : flag (empty)

Turns off exercise auto numbering.

• hidden : flag (empty)

Removes the directive from the final output.

Example

Exercise 1

Recall that $$n!$$ is read as “$$n$$ factorial” and defined as $$n! = n \times (n - 1) \times \cdots \times 2 \times 1$$.

There are functions to compute this in various modules, but let’s write our own version as an exercise.

In particular, write a function factorial such that factorial(n) returns $$n!$$ for any positive integer $$n$$.

MyST Syntax

{exercise}
:label: my-exercise

Recall that $n!$ is read as "$n$ factorial" and defined as
$n! = n \times (n - 1) \times \cdots \times 2 \times 1$.

There are functions to compute this in various modules, but let's
write our own version as an exercise.

In particular, write a function factorial such that factorial(n) returns $n!$
for any positive integer $n$.



Source: QuantEcon

### Referencing Exercises¶

You can refer to an exercise using the {ref} role like {ref}my-exercise , which will display the title of the exercise directive. In the event that directive does not have a title, the title will be the default “Exercise” or “Exercise {number}” like so: Exercise 1.

Enumerable directives can also be referenced through the numref role like {numref}my-exercise , which will display the number of the exercise directive. Referencing the above directive will display Exercise 1. In this case it displays the same result as the {ref} role as exerise notes are (by default) enumerated.

Furthermore, numref can take in three additional placeholders for more customized titles:

1. %s

2. {number} which get replaced by the exercise number, and

3. {name} by the exercise title.1

An example {numref}My custom {number} title and {name}  would resolve to My custom 1 title and Exercise

## Solution Directive¶

A solution directive can be included using the solution pattern. It takes in the label of the directive it wants to link to as a required argument. Unlike the exercise directive, the solution directive not enumerable as it inherits directly from the linked exercise.

The following options are also supported:

• label : text

A unique identifier for your solution that you can use to reference it with {ref}. Cannot contain spaces or special characters.

• class : text

Value of the solution’s class attribute which can be used to add custom CSS or JavaScript.

• hidden : flag (empty)

Removes the directive from the final output.

Example

Solution to Exercise 1

Here’s one solution.

def factorial(n):
k = 1
for i in range(n):
k = k * (i + 1)
return k

factorial(4)


MyST Syntax

{solution} my-exercise
:label: my-solution

Here's one solution.

{code-block} python
def factorial(n):
k = 1
for i in range(n):
k = k * (i + 1)
return k

factorial(4)




Source: QuantEcon

## Alternative Gated Syntax¶

A restriction of MyST is that code-cell directives must be at the root level of the document for them to be executed. This maintains direct compatility with the jupyter notebook and enables tools like jupytext to convert between myst and ipynb files.

As a result executable code-cell directives cannot be nested inside of exercises or solution directives.

The solution to this is to use the gated syntax.

Note

This syntax can also be a convenient way of surrounding blocks of text that may include other directives that you wish to include in an exercise or solution admonition.

### Basic Syntax¶

{exercise-start}
:label: ex1


{code-cell}
# Some setup code that needs executing


and maybe you wish to add a figure

{figure} img/example.png


{exercise-end}



The exercise-start directive allows for he same options as core exercise directive.

{solution-start} ex1


{code-cell}
# Solution Code


{solution-end}



Warning

If there are missing -start and -end directives, this will cause Sphinx to return an extension error, alongside some helpful feedback to diagnose the issue in document structure.

### Example¶

{solution-start} exercise-1
:label: solution-gated-1


This is a solution to Exercise 1

{code-cell} python3
import numpy as np
import matplotlib.pyplot as plt

# Fixing random state for reproducibility
np.random.seed(19680801)

dt = 0.01
t = np.arange(0, 30, dt)
nse1 = np.random.randn(len(t))                 # white noise 1
nse2 = np.random.randn(len(t))                 # white noise 2

# Two signals with a coherent part at 10Hz and a random part
s1 = np.sin(2 * np.pi * 10 * t) + nse1
s2 = np.sin(2 * np.pi * 10 * t) + nse2

fig, axs = plt.subplots(2, 1)
axs[0].plot(t, s1, t, s2)
axs[0].set_xlim(0, 2)
axs[0].set_xlabel('time')
axs[0].set_ylabel('s1 and s2')
axs[0].grid(True)

cxy, f = axs[1].cohere(s1, s2, 256, 1. / dt)
axs[1].set_ylabel('coherence')

fig.tight_layout()
plt.show()


With some follow up text to the solution

{solution-end}



will produce the following solution block in your html output.

### Referencing Solutions¶

You can refer to a solution using the {ref} role like: {ref}my-solution  the output of which depends on the attributes of the linked directive. If the linked directive is enumerable, the role will replace the solution reference with the linked directive type and its appropriate number like so: Solution to Exercise 1.

In the event that the directive being referenced is unenumerable, the reference will display its title: Solution to Exercise (n! Factorial). Click the toggle to see the supporting directives.

Exercise ($$n!$$ Factorial)

Write a function factorial such that factorial(int n) returns $$n!$$ for any positive integer $$n$$.

Solution to Exercise ($$n!$$ Factorial)

Here’s a solution in Java.

static int factorial(int n){
if (n == 0)
return 1;
else {
return(n * factorial(n-1));
}
}


If the title of the linked directive being reference does not exist, it will default to Solution to Exercise. Click the toggle to see the supporting directives.

Exercise

Write a function factorial such that factorial(int n) returns $$n!$$ for any positive integer $$n$$.

Solution to Exercise

Here’s a solution in Java.

static int factorial(int n){
if (n == 0)
return 1;
else {
return(n * factorial(n-1));
}
}


## Hide or Remove Directives¶

### Hide Content¶

The content of directives can be hidden using the dropdown class which is available through sphinx-togglebutton. For Sphinx projects, add "sphinx_togglebutton" to your extensions list in conf.py to activate the extension

extensions = [
...
"sphinx_togglebutton"
...
]


For Jupyter Book projects, add sphinx_togglebutton under extra_extensions

sphinx:
extra_extensions:
- sphinx_togglebutton


To hide the content, simply add :class: dropdown as a directive option.

For more use cases see sphinx-togglebutton.

Example

MyST Syntax:

{exercise}
:class: dropdown

Recall that $n!$ is read as "$n$ factorial" and defined as
$n! = n \times (n - 1) \times \cdots \times 2 \times 1$.

There are functions to compute this in various modules, but let's
write our own version as an exercise.

In particular, write a function factorial such that factorial(n) returns $n!$
for any positive integer $n$.



### Remove Directives¶

Any specific directive can be hidden by introducing the :hidden: option. For example, the following example will not be displayed

{exercise}
:hidden:

This is a hidden exercise directive.



### Remove All Solutions¶

All solution directives can be removed from the final output by setting hide_solutions to True. For Sphinx projects, add the configuration key in the conf.py file. Jupyter Book projects, should set the configuration key in _config.yml as follows

...
sphinx:
config:
hide_solutions: True
...


## Custom CSS or JavaScript¶

Custom JavaScript scripts and CSS rules will allow you to add additional functionality or customize how elements are displayed. If you’d like to include custom CSS or JavaScript scripts in Jupyter Book, simply add any files ending in .css or .js under a _static folder. Any files under this folder will be automatically copied into the built book.

In Sphinx, this can be achieved by specifying the path of your _static folder and including CSS/JavaScript files by using the options html_css_files and html_js_files in conf.py:

# conf.py

html_static_path = ["_static"]

# CSS files
html_css_files = ["custom.css",]
# JS files
html_js_files = ["custom.js",]


For example, to include the following CSS content which changes the default color of an exercise directive named “orange” under docs/_static/custom.css:

/* docs/_static/custom.css */

:root {
--background-color: rgba(253, 126, 20, .3);
--border-color: #fd7e14;
}

div.orange {
background-color: var(--background-color);
border-color: var(--border-color);
}

background-color: var(--background-color);
}


Add html_static_path and html_css_files under conf.py:

# conf.py

html_static_path = ['../_static']
html_css_files = ['custom.css']


These steps will change the default color of the exercise directive named “orange” displayed below

{exercise}
:class: orange

This is an example of how to introduce custom CSS.



Exercise 3

This is an example of how to introduce custom CSS.

1

If the exercise directive does not have a title, an invalid numfig format warning will be displayed during build if the user tries to use the {name} placeholder.