spawneditor

A Python module that attempts to provide a common interface for opening an editor at a specified line in a file.

The launched editor will be chosen from, in order:

1. The explicitly specified editor.
2. The VISUAL environment variable, if DISPLAY is available.
3. The EDITOR environment variable.
4. Hard-coded paths to common editors.

Installation

pip install --user spawneditor

Alternatively clone the Git repository as a Git submodule named spawneditor.

Examples

import spawneditor

# Open an existing file in the default editor.
spawneditor.edit_file("path/to/file.txt")

# A line number may be specified.
spawneditor.edit_file("path/to/file.txt", line_number=123)

# Edits a blank temporary file.
edited_lines = spawneditor.edit_temporary()  

# Edits a temporary file with specified content.  Unlike `edit_file`,
# `edit_temporary` returns the contents of the edited file.
instructions = [
    "Instructions:",
    "Enter some text below the line.",
    "----",
]
new_contents = spawneditor.edit_temporary(instructions,
                                          line_number=(len(instructions) + 1))

# ... or, if you prefer a single string with newlines:
new_contents = spawneditor.edit_temporary(
    sss["Instructions:\nEnter some text below the line.\n----"],
    line_number=4,
)

for line in new_contents:
    print(line, end="")

FAQ

Q: How does spawneditor know how to invoke the editor at a specified line number?

spawneditor is hard-coded to recognize and invoke some common editors based on the name of the executed binary.

Q: What is considered a "common editor"?

See the editor_syntax_table in spawneditor.py.

Q: What if my editor isn't supported?

Other editors should still work. At worst, the specified file should be opened in the default editor, just not at the specified line.

If your editor isn't supported, I also encourage filing an issue or pull request to add support.

Q: Why not provide some mechanism for end-users to specify the syntax for their editor?

It's tempting to support using, say, a configuration file to allow users to specify how to invoke arbitrary editors. I currently prefer not to because:

• It adds code complexity and incurs a penalty for what is likely to be a rare situation.
• It reduces incentives to make spawneditor support other editors directly.
• The fallback behavior still should open the file in the default editor, just not at the specified line number. I think that's pretty acceptable.

One pathological situation where an override would be necessary is if an editor uses the same executable name as one of the recognized editors and uses a different command-line syntax for specifying the line number. However, that also should be a very rare situation.

One compelling reason might be to allow people to set their default editor to a wrapper script that invokes their actual editor. I'm sympathetic to that, but in the meantime, the wrapper script could be given the same name as the actual editor.

Q: Why does VISUAL depend on DISPLAY?

Technically VISUAL should refer to a full-screen editor, not necessarily a graphical editor. In practice, however, I think that the graphical vs. text-mode distinction is far more relevant and important than the distinction between full-screen and line-based editors.

Q: Why does spawneditor.edit_file immediately return when spawning a multi-document editor (e.g. Visual Studio Code, Sublime Text)?

Multi-document editors are typically also single-instance: when the editor is invoked, a new process will be spawned, but that process then will forward the request to an existing, primary process. The new, secondary process then will immediately exit and cause spawneditor.edit_file to return. Such editors typically provide a command-line option (e.g. --wait for Visual Studio Code and Sublime Text) to keep the secondary process alive until the file is closed by the primary process. Consult the documentation to your editor.

Q: Aren't there already Python packages that do this?

Yes. The editor and python-editor packages are alternatives that also invoke the default editor. Currently neither one supports opening a file to a specified line number. Were I aware of them when I wrote spawneditor, and possibly I would have tried contributing to them instead. However, spawneditor is implemented rather differently than either one, and I'm not sure that either project would have appreciated drastic changes. There likely is room for cross-pollination.

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Copyright © 2020-2022 James D. Lin.