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nushell/crates/nu_plugin_python/nu_plugin_python_example.py

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# Example of using a Python script as a Nushell plugin
#
# The example uses JSON encoding but it should be a similar process using
# msgpack to move data between Nushell and the plugin. The only difference
# would be that you need to use msgpack relative lib(like msgpack) to
# decode and encode information that is read and written to stdin and stdout
#
# To register the plugin use:
# register <path-to-py-file>
#
# Be carefull with the spans. Miette will crash if a span is outside the
# size of the contents vector. For this example we are using 0 and 1, which will
# point to the beginning of the contents vector. We strongly suggest using the span
# found in the plugin call head
#
# The plugin will be run using the active Python implementation. If you are in
# a Python environment, that is the Python version that is used
#
# Note: To keep the plugin simple and without dependencies, the dictionaries that
# represent the data transferred between Nushell and the plugin are kept as
# native Python dictionaries. The encoding and decoding process could be improved
# by using libraries like pydantic and marshmallow
#
# This plugin uses python3
# Note: To debug plugins write to stderr using sys.stderr.write
import sys
import json
def signatures():
"""
Multiple signatures can be sent to Nushell. Each signature will be registered
as a different plugin function in Nushell.
In your plugin logic you can use the name of the signature to indicate what
operation should be done with the plugin
"""
return {
"Signature": [
{
"name": "nu-python",
"usage": "Signature test for Python",
"extra_usage": "",
"input_type": "Any",
"output_type": "Any",
"required_positional": [
{
"name": "a",
"desc": "required integer value",
"shape": "Int",
"var_id": None,
},
{
"name": "b",
"desc": "required string value",
"shape": "String",
"var_id": None,
},
],
"optional_positional": [
{
"name": "opt",
"desc": "Optional number",
"shape": "Int",
"var_id": None,
}
],
"rest_positional": {
"name": "rest",
"desc": "rest value string",
"shape": "String",
"var_id": None,
},
"named": [
{
"long": "help",
"short": "h",
"arg": None,
"required": False,
"desc": "Display the help message for this command",
"var_id": None
},
{
"long": "flag",
"short": "f",
"arg": None,
"required": False,
"desc": "a flag for the signature",
"var_id": None,
},
{
"long": "named",
"short": "n",
"arg": "String",
"required": False,
"desc": "named string",
"var_id": None,
},
],
"search_terms": ["Python", "Example"],
"is_filter": False,
"creates_scope": False,
"category": "Experimental",
}
]
}
def process_call(plugin_call):
"""
plugin_call is a dictionary with the information from the call
It should contain:
- The name of the call
- The call data which includes the positional and named values
- The input from the pipeline
Use this information to implement your plugin logic
"""
# Pretty printing the call to stderr
sys.stderr.write(json.dumps(plugin_call, indent=4))
sys.stderr.write("\n")
# Creates a Value of type List that will be encoded and sent to Nushell
return {
"Value": {
"List": {
"vals": [
{
"Record": {
"cols": ["one", "two", "three"],
"vals": [
{
"Int": {
"val": 0,
"span": {"start": 0, "end": 1},
}
},
{
"Int": {
"val": 0,
"span": {"start": 0, "end": 1},
}
},
{
"Int": {
"val": 0,
"span": {"start": 0, "end": 1},
}
},
],
"span": {"start": 0, "end": 1},
}
},
{
"Record": {
"cols": ["one", "two", "three"],
"vals": [
{
"Int": {
"val": 0,
"span": {"start": 0, "end": 1},
}
},
{
"Int": {
"val": 1,
"span": {"start": 0, "end": 1},
}
},
{
"Int": {
"val": 2,
"span": {"start": 0, "end": 1},
}
},
],
"span": {"start": 0, "end": 1},
}
},
{
"Record": {
"cols": ["one", "two", "three"],
"vals": [
{
"Int": {
"val": 0,
"span": {"start": 0, "end": 1},
}
},
{
"Int": {
"val": 2,
"span": {"start": 0, "end": 1},
}
},
{
"Int": {
"val": 4,
"span": {"start": 0, "end": 1},
}
},
],
"span": {"start": 0, "end": 1},
}
},
{
"Record": {
"cols": ["one", "two", "three"],
"vals": [
{
"Int": {
"val": 0,
"span": {"start": 0, "end": 1},
}
},
{
"Int": {
"val": 3,
"span": {"start": 0, "end": 1},
}
},
{
"Int": {
"val": 6,
"span": {"start": 0, "end": 1},
}
},
],
"span": {"start": 0, "end": 1},
}
},
{
"Record": {
"cols": ["one", "two", "three"],
"vals": [
{
"Int": {
"val": 0,
"span": {"start": 0, "end": 1},
}
},
{
"Int": {
"val": 4,
"span": {"start": 0, "end": 1},
}
},
{
"Int": {
"val": 8,
"span": {"start": 0, "end": 1},
}
},
],
"span": {"start": 0, "end": 1},
}
},
{
"Record": {
"cols": ["one", "two", "three"],
"vals": [
{
"Int": {
"val": 0,
"span": {"start": 0, "end": 1},
}
},
{
"Int": {
"val": 5,
"span": {"start": 0, "end": 1},
}
},
{
"Int": {
"val": 10,
"span": {"start": 0, "end": 1},
}
},
],
"span": {"start": 0, "end": 1},
}
},
{
"Record": {
"cols": ["one", "two", "three"],
"vals": [
{
"Int": {
"val": 0,
"span": {"start": 0, "end": 1},
}
},
{
"Int": {
"val": 6,
"span": {"start": 0, "end": 1},
}
},
{
"Int": {
"val": 12,
"span": {"start": 0, "end": 1},
}
},
],
"span": {"start": 0, "end": 1},
}
},
{
"Record": {
"cols": ["one", "two", "three"],
"vals": [
{
"Int": {
"val": 0,
"span": {"start": 0, "end": 1},
}
},
{
"Int": {
"val": 7,
"span": {"start": 0, "end": 1},
}
},
{
"Int": {
"val": 14,
"span": {"start": 0, "end": 1},
}
},
],
"span": {"start": 0, "end": 1},
}
},
{
"Record": {
"cols": ["one", "two", "three"],
"vals": [
{
"Int": {
"val": 0,
"span": {"start": 0, "end": 1},
}
},
{
"Int": {
"val": 8,
"span": {"start": 0, "end": 1},
}
},
{
"Int": {
"val": 16,
"span": {"start": 0, "end": 1},
}
},
],
"span": {"start": 0, "end": 1},
}
},
{
"Record": {
"cols": ["one", "two", "three"],
"vals": [
{
"Int": {
"val": 0,
"span": {"start": 0, "end": 1},
}
},
{
"Int": {
"val": 9,
"span": {"start": 0, "end": 1},
}
},
{
"Int": {
"val": 18,
"span": {"start": 0, "end": 1},
}
},
],
"span": {"start": 0, "end": 1},
}
},
],
"span": {"start": 0, "end": 1},
}
}
}
def tell_nushell_encoding():
sys.stdout.write(chr(4))
for ch in "json":
sys.stdout.write(chr(ord(ch)))
sys.stdout.flush()
def plugin():
tell_nushell_encoding()
call_str = ",".join(sys.stdin.readlines())
plugin_call = json.loads(call_str)
if plugin_call == "Signature":
signature = json.dumps(signatures())
sys.stdout.write(signature)
elif "CallInfo" in plugin_call:
response = process_call(plugin_call)
sys.stdout.write(json.dumps(response))
else:
# Use this error format if you want to return an error back to Nushell
error = {
"Error": {
"label": "ERROR from plugin",
"msg": "error message pointing to call head span",
"span": {"start": 0, "end": 1},
}
}
sys.stdout.write(json.dumps(error))
if __name__ == "__main__":
plugin()
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