Managing Execution Environments

Introduction

Interactive coding in Quarto Live supports both a global environment and isolated exercise environments. This flexibility lets you share variables across code blocks or isolate code in exercises to prevent interference.

Global Environment

Non-exercise interactive code blocks run in the global environment. Variables defined in one block are available in subsequent blocks. For example:

Source Code

```{webr}
#| autorun: true
# A non-exercise code block: global environment
foo <- c(1, 3, 5, 7)
```

```{webr}
# Another block accessing the variable 'foo' from the global environment
foo + 42
```

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# A non-exercise code block: global environment

foo <- c(1, 3, 5, 7)

_webr_editor_1 = Object {code: "# A non-exercise code block: global environment\nfoo <- c(1, 3, 5, 7)", options: Object, indicator: Ke}

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# Another block accessing the variable 'foo' from the global environment

foo + 42

_webr_editor_2 = Object {code: null, options: Object, indicator: Ke}

Exercise Environments

By default, interactive exercises are evaluated in isolated environments. This prevents variables defined in one exercise from affecting others.

Source Code

```{webr}
#| exercise: ex_1
#| setup: true
# Variables defined in an exercise setup block are isolated to that exercise
bar <- c(2, 4, 6, 8)
```

```{webr}
#| exercise: ex_1
#| autorun: true
# The exercise can access both its own variables and those from the global environment (e.g., 'foo')
foo
bar
```

```{webr}
#| autorun: true
# This global code block cannot access variables from the exercise environment
bar
```

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# The exercise can access both its own variables and those from the global environment (e.g., 'foo')

foo

bar

_webr_editor_4 = Object {code: "# The exercise can access both its own variables a…from the global environment (e.g., 'foo')\nfoo\nbar", options: Object, indicator: Ke}

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# This global code block cannot access variables from the exercise environment

bar

_webr_editor_5 = Object {code: "# This global code block cannot access variables from the exercise environment\nbar", options: Object, indicator: Ke}

Manually Managing Environments

Sometimes, you may want to share variables between exercises. You can do this by assigning a common environment using the envir option. For example, specifying envir: myenv in multiple exercise code blocks causes them to share the same environment:

Source Code

```{webr}
#| envir: myenv
#| exercise: ex_shared_1
#| autorun: true
abc <- 7
```

```{webr}
#| envir: myenv
#| exercise: ex_shared_2
#| autorun: true
xyz <- 5
```

```{webr}
#| envir: myenv
#| exercise: ex_shared_3
#| autorun: true
abc + xyz
```

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abc <- 7

_webr_editor_6 = Object {code: "abc <- 7", options: Object, indicator: Ke}

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xyz <- 5

_webr_editor_7 = Object {code: "xyz <- 5", options: Object, indicator: Ke}

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abc + xyz

_webr_editor_8 = Object {code: "abc + xyz", options: Object, indicator: Ke}

Conclusion

By understanding the differences between the global and exercise environments, you can effectively control variable sharing and isolation in your interactive documents. Whether using the default global settings or manually managing environments with the envir option, these techniques help ensure that your interactive code behaves as expected.

Further Reading

• Interactive Code Blocks Explained
  Explore how to create and customize interactive code blocks using the webr and pyodide engines.

• Loading and Using Packages
  Learn how to install and use additional R and Python packages in interactive documents.

• Plotting and Graphics
  Discover techniques for creating dynamic visualizations and customizing plot dimensions in interactive code blocks.

• Cell Options Reference
  For a complete list of all available cell options and advanced configurations in Quarto Live.

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