# Inline variable evaluation (eval)#

New in version 0.15.0.

The eval submodule allows you to insert code variables directly into the text flow of your documentation.

Use of eval requires that the notebook execution mode is set to inline, since the variables are evaluated by the notebook kernel. For example, using the top-matter:

---
file_format: mystnb
kernelspec:
name: python3
mystnb:
execution_mode: 'inline'
---


## Basic example#

Below we set a variable v1 within a code cell.

v1 = "My variable"


Using the eval role, we can insert the variable v1 into the text of a paragraph:

{eval}v1 -> My variable

If we update the variable, we can see the change reflected in subsequent evaluation:

v1 = "My new variable"


{eval}v1 -> My new variable

Important

Variable names must match the regex [a-zA-Z][a-zA-Z0-9_]*

## Inserting different output types#

Any variable type can be inserted into the text flow using the eval role, and the most suitable output type will be used, based on the output format (see Outputs MIME priority for more information). For example:

import ipywidgets as widgets
slider = widgets.IntSlider(value=5, min=0, max=10)


An inline slider ({eval}slider):

You can also use the eval directive to insert variables as blocks:

import matplotlib.pyplot as plt
myplot, ax = plt.subplots(figsize=(6, 2))
mean = 2.0
ax.plot([1,2,3])
ax.grid()
plt.close()


using:

{eval} myplot



gives:

## Embedding outputs in figures#

The eval:figure directive allows you to embed outputs in a figure, with an optional caption and other formatting options.

For example, we can embed the output of the above plot in a figure:

{eval:figure} myplot
:name: myplot
My plot with a mean value of {eval}mean.



which gives:

That can be referenced with {ref}myplot: My plot with a mean value of 2.0.

The following directive options are available:

eval:figure directive options#

Option

Type

Description

figwidth

length or percentage

The width of the figure

figclass

text

A space-separated list of class names for the figure

name

text

referenceable label for the figure

alt

text

Alternate text of an image

height

length

The desired height of an image

width

length or percentage

The width of an image

scale

percentage

The uniform scaling factor of an image

class

text

A space-separated list of class names for the image

align

text

left, center, or right