ENH: Add Monte Carlo outputs export to CSV/JSON (#242) #912

GMinoruy · 2025-12-07T22:25:13Z

Pull request type

Code changes (bugfix, features)

Checklist

Implement export functionality for .csv.
Implement export functionality for .json.
Ensure that export_list and custom data_collector variables are included in the export.
Add unit tests in tests/ ensuring the files are created and contain correct data.
Update the documentation to include examples of how to export data.

Current behavior

Currently the MonteCarlo class saves the simulation results into .outputs.txt files. There is no method that allowa users to export these results into .csv or .json files. See issue #242.

New behavior

Implements the export_results method in the MonteCarlo class. This method reads the data from .outputs.txt files and rewrites them to .csv and .json format, based on the user`s selection

Breaking change

Yes
No

Copilot

Pull request overview

This pull request adds CSV and JSON export functionality to the MonteCarlo class, addressing issue #242. The enhancement allows users to convert Monte Carlo simulation results from the default .outputs.txt format to more widely-used .csv and .json formats for easier data analysis and integration with external tools.

Key Changes

Added export_results() method to MonteCarlo class that reads .outputs.txt files and exports to CSV or JSON format based on user selection
Included unit test to verify file creation for both CSV and JSON exports
Updated documentation with usage examples in the Monte Carlo analysis notebook

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 13 comments.

File	Description
rocketpy/simulation/monte_carlo.py	Implements the `export_results()` method with CSV/JSON conversion logic using `csv.DictWriter` and `json.dump`
tests/unit/simulation/test_monte_carlo.py	Adds unit test that verifies CSV and JSON files are created, includes mock data setup and file cleanup
docs/notebooks/monte_carlo_analysis/monte_carlo_class_usage.ipynb	Adds documentation section demonstrating how to use the new export functionality with example code

Copilot · 2025-12-09T00:19:59Z

tests/unit/simulation/test_monte_carlo.py

        mc.estimate_confidence_interval("apogee", statistic="not_a_function")
+
+
+def test_monte_carlo_export_results_to_csv_and_json_files(monte_carlo_calisto, tmp_path):


Test function name could be more descriptive and follow the pattern test_methodname_expectedbehaviour. Consider renaming to test_export_results_creates_csv_and_json_files to better indicate what method is being tested and what behavior is expected.

Suggested change

def test_monte_carlo_export_results_to_csv_and_json_files(monte_carlo_calisto, tmp_path):

def test_export_results_creates_csv_and_json_files(monte_carlo_calisto, tmp_path):

Copilot · 2025-12-09T00:20:00Z

tests/unit/simulation/test_monte_carlo.py

+        assert expected_file_in_csv.exists()
+
+        mc.export_results(tmp_path / "mock_output_in_json", "json")
+        expected_file_in_json = tmp_path / f"{"mock_output_in_json"}.json"


Unnecessary f-string usage. The expression f"{"mock_output_in_json"}" is redundant and can be simplified to just "mock_output_in_json".

Suggested change

expected_file_in_json = tmp_path / f"{"mock_output_in_json"}.json"

expected_file_in_json = tmp_path / "mock_output_in_json.json"

Copilot · 2025-12-09T00:20:00Z

tests/unit/simulation/test_monte_carlo.py

+        mc.export_results(tmp_path / "mock_outputs_in_csv", "csv")
+        expected_file_in_csv = tmp_path / f"{"mock_outputs_in_csv"}.csv"
+        assert expected_file_in_csv.exists()
+
+        mc.export_results(tmp_path / "mock_output_in_json", "json")
+        expected_file_in_json = tmp_path / f"{"mock_output_in_json"}.json"
+        assert expected_file_in_json.exists()


The test only verifies that files are created but doesn't validate their contents. Consider adding assertions to:

Verify the CSV/JSON files contain the expected mock data (apogee: 100, max_velocity: 255)

Check CSV header format

Verify JSON structure and indentation

Example:

# For CSV import csv with open(expected_file_in_csv, "r") as f: reader = csv.DictReader(f) rows = list(reader) assert len(rows) == 1 assert rows[0]["apogee"] == "100" assert rows[0]["max_velocity"] == "255" # For JSON with open(expected_file_in_json, "r") as f: data = json.load(f) assert len(data) == 1 assert data[0]["apogee"] == 100 assert data[0]["max_velocity"] == 255

Copilot · 2025-12-09T00:20:00Z

tests/unit/simulation/test_monte_carlo.py

+def test_monte_carlo_export_results_to_csv_and_json_files(monte_carlo_calisto, tmp_path):
+    """Checks that the export_results create .csv and .json files
+
+    Parameters
+    ----------
+    monte_carlo_calisto : MonteCarlo
+        Fixture that has the .txt files necessary for the export_results
+    """
+    try:
+        mc = monte_carlo_calisto
+        mc.filename = tmp_path / "mock_output"
+        mock_data = {"apogee": 100, "max_velocity": 255}
+        with open(tmp_path / "mock_output.outputs.txt", "w") as f:
+            f.write(json.dumps(mock_data) + "\n")
+
+        mc.export_results(tmp_path / "mock_outputs_in_csv", "csv")
+        expected_file_in_csv = tmp_path / f"{"mock_outputs_in_csv"}.csv"
+        assert expected_file_in_csv.exists()
+
+        mc.export_results(tmp_path / "mock_output_in_json", "json")
+        expected_file_in_json = tmp_path / f"{"mock_output_in_json"}.json"
+        assert expected_file_in_json.exists()
+    finally:
+        os.remove("monte_carlo_test.errors.txt")
+        os.remove("monte_carlo_test.inputs.txt")
+        os.remove("monte_carlo_test.outputs.txt")


The test doesn't cover important edge cases and error conditions:

Invalid output_format parameter (e.g., "xml", "pdf")

Non-existent .outputs.txt file

Empty .outputs.txt file

Malformed JSON in .outputs.txt file

Case insensitivity of output_format (e.g., "CSV", "Json")

Consider adding separate test cases for these scenarios to ensure the method handles errors gracefully.

Copilot · 2025-12-09T00:20:01Z

tests/unit/simulation/test_monte_carlo.py

+        os.remove("monte_carlo_test.errors.txt")
+        os.remove("monte_carlo_test.inputs.txt")
+        os.remove("monte_carlo_test.outputs.txt")


File cleanup in the finally block will fail if the files don't exist. This can happen if the fixture fails to create these files or if the test is run in isolation. Use os.path.exists() checks or use a helper function similar to _post_test_file_cleanup() found in integration tests (see tests/integration/simulation/test_monte_carlo.py:12-25).

Suggested fix:

finally: for filepath in ["monte_carlo_test.errors.txt", "monte_carlo_test.inputs.txt", "monte_carlo_test.outputs.txt"]: if os.path.exists(filepath): os.remove(filepath)

Suggested change

os.remove("monte_carlo_test.errors.txt")

os.remove("monte_carlo_test.inputs.txt")

os.remove("monte_carlo_test.outputs.txt")

for filepath in [

"monte_carlo_test.errors.txt",

"monte_carlo_test.inputs.txt",

"monte_carlo_test.outputs.txt",

]:

if os.path.exists(filepath):

os.remove(filepath)

Copilot · 2025-12-09T00:20:02Z

rocketpy/simulation/monte_carlo.py

+        with open(f"{self.filename}.outputs.txt", "r", encoding="utf-8") as f:
+            for line in f:
+                line = line.strip()
+                data = json.loads(line)
+                txt_data.append(data)


Missing error handling for file I/O operations. The method should handle FileNotFoundError when the .outputs.txt file doesn't exist and provide a clear error message to the user. Additionally, consider handling json.JSONDecodeError if the file contains malformed JSON data.

Suggested change

with open(f"{self.filename}.outputs.txt", "r", encoding="utf-8") as f:

for line in f:

line = line.strip()

data = json.loads(line)

txt_data.append(data)

try:

with open(f"{self.filename}.outputs.txt", "r", encoding="utf-8") as f:

for line_number, line in enumerate(f, start=1):

line = line.strip()

try:

data = json.loads(line)

txt_data.append(data)

except json.JSONDecodeError as e:

_SimMonitor.reprint(

f"Error decoding JSON on line {line_number} of '{self.filename}.outputs.txt': {e}\n"

f"Line content: {line}\n"

"Please check the file for malformed JSON data."

)

raise

except FileNotFoundError:

_SimMonitor.reprint(

f"File '{self.filename}.outputs.txt' not found. "

"Please ensure that the Monte Carlo simulation has been run and the output file exists."

)

raise

Copilot · 2025-12-09T00:20:02Z

rocketpy/simulation/monte_carlo.py

+                json.dump(txt_data, f, indent=4)
+                _SimMonitor.reprint(f"Results saved to {Path(output_filename)} as .json file")
+        elif output_format == "csv":
+            output_csv_header = txt_data[0].keys()


Potential IndexError if txt_data is empty. If the .outputs.txt file is empty or contains only blank lines, txt_data[0] will raise an IndexError. Add validation to check that txt_data is not empty before attempting to access its first element.

Copilot · 2025-12-09T00:20:02Z

rocketpy/simulation/monte_carlo.py

+                _SimMonitor.reprint(f"Results saved to {Path(output_filename)} as .json file")
+        elif output_format == "csv":
+            output_csv_header = txt_data[0].keys()
+            with open(f"{output_filename}.csv", "w", newline= "") as f:


Extra space before empty string in newline= "" parameter. Should be newline="" (no space before the equals sign) to follow Python style conventions (PEP 8).

Suggested change

with open(f"{output_filename}.csv", "w", newline= "") as f:

with open(f"{output_filename}.csv", "w", newline="") as f:

Copilot · 2025-12-09T00:20:02Z

rocketpy/simulation/monte_carlo.py

+        """Converts the default Monte Carlo .txt output to .cvs or .json file
+        depending on the user's choice
+
+        Parameters
+        ----------
+        output_filename : str
+            Name of the file in which the converted data will be saved
+        output_format : str
+            Format of the output file
+
+        Returns
+        -------
+        None


The docstring is missing important details. It should:

Specify that output_filename can be a string or Path object

Document the valid values for output_format ("csv" or "json")

Explain what happens if the output file already exists (will it be overwritten?)

Mention that the method reads from self.filename.outputs.txt

Follow NumPy docstring format with a proper description section before Parameters

Example improvement:

\"\"\"Export Monte Carlo simulation results to CSV or JSON format. This method reads simulation output data from the `.outputs.txt` file and converts it to either CSV or JSON format based on user selection. Parameters ---------- output_filename : str or Path Path and name of the output file (without extension). The appropriate extension (.csv or .json) will be added automatically. output_format : str Format of the output file. Must be either "csv" or "json" (case-insensitive). Returns ------- None Raises ------ FileNotFoundError If the `.outputs.txt` file does not exist. ValueError If `output_format` is not "csv" or "json". \"\"\"

Suggested change

"""Converts the default Monte Carlo .txt output to .cvs or .json file

depending on the user's choice

Parameters

----------

output_filename : str

Name of the file in which the converted data will be saved

output_format : str

Format of the output file

Returns

-------

None

"""Export Monte Carlo simulation results to CSV or JSON format.

This method reads simulation output data from the `.outputs.txt` file

(specifically, from `self.filename.outputs.txt`) and converts it to either

CSV or JSON format based on user selection. The output file will be

overwritten if it already exists.

Parameters

----------

output_filename : str or Path

Path and name of the output file (without extension). The appropriate

extension (.csv or .json) will be added automatically.

output_format : str

Format of the output file. Must be either "csv" or "json"

(case-insensitive).

Returns

-------

None

Raises

------

FileNotFoundError

If the `.outputs.txt` file does not exist.

ValueError

If `output_format` is not "csv" or "json".

Examples

--------

>>> mc.export_results("results", "csv")

>>> mc.export_results(Path("results_folder/results"), "json")

Copilot · 2025-12-09T00:20:03Z

tests/unit/simulation/test_monte_carlo.py

+        expected_file_in_csv = tmp_path / f"{"mock_outputs_in_csv"}.csv"
+        assert expected_file_in_csv.exists()
+
+        mc.export_results(tmp_path / "mock_output_in_json", "json")
+        expected_file_in_json = tmp_path / f"{"mock_output_in_json"}.json"


Unnecessary f-string usage. The expression f"{"mock_outputs_in_csv"}" is redundant and can be simplified to just "mock_outputs_in_csv". The same applies to line 212.

Suggested change

expected_file_in_csv = tmp_path / f"{"mock_outputs_in_csv"}.csv"

assert expected_file_in_csv.exists()

mc.export_results(tmp_path / "mock_output_in_json", "json")

expected_file_in_json = tmp_path / f"{"mock_output_in_json"}.json"

expected_file_in_csv = tmp_path / "mock_outputs_in_csv.csv"

assert expected_file_in_csv.exists()

mc.export_results(tmp_path / "mock_output_in_json", "json")

expected_file_in_json = tmp_path / "mock_output_in_json.json"

…tPy-Team#242

GMinoruy requested a review from a team as a code owner December 7, 2025 22:25

Gui-FernandesBR force-pushed the enh/issue-242-monte-carlo-outputs branch 2 times, most recently from e3473df to f38ac20 Compare December 9, 2025 00:13

Gui-FernandesBR requested a review from Copilot December 9, 2025 00:14

Copilot started reviewing on behalf of Gui-FernandesBR December 9, 2025 00:14 View session

Copilot AI reviewed Dec 9, 2025

View reviewed changes

Gui-FernandesBR linked an issue Dec 9, 2025 that may be closed by this pull request

ENH: Save Monte Carlo outputs to .csv and .json formats #242

Open

5 tasks

GMinoruy added 6 commits December 9, 2025 09:41

ENH: trying to add Monte Carlo output to csv and json see issue Rocke…

e51b221

…tPy-Team#242

ENH: corrects errors identified during testing

fe7c69e

ENH: adds example on how to use the export_results function

1c1c77a

ENH: adds visual feedback when exporting in csv and json

ee4bab5

ENH: adds Docstring to the function

d0cc223

ENH: adds unit test of the function export_results

6503273

Gui-FernandesBR force-pushed the enh/issue-242-monte-carlo-outputs branch from f38ac20 to 6503273 Compare December 9, 2025 12:41

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ENH: Add Monte Carlo outputs export to CSV/JSON (#242) #912

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		mc.estimate_confidence_interval("apogee", statistic="not_a_function")


		def test_monte_carlo_export_results_to_csv_and_json_files(monte_carlo_calisto, tmp_path):

	def test_monte_carlo_export_results_to_csv_and_json_files(monte_carlo_calisto, tmp_path):
	def test_export_results_creates_csv_and_json_files(monte_carlo_calisto, tmp_path):

	expected_file_in_json = tmp_path / f"{"mock_output_in_json"}.json"
	expected_file_in_json = tmp_path / "mock_output_in_json.json"

-        os.remove("monte_carlo_test.errors.txt")
-        os.remove("monte_carlo_test.inputs.txt")
-        os.remove("monte_carlo_test.outputs.txt")
+        for filepath in [
+            "monte_carlo_test.errors.txt",
+            "monte_carlo_test.inputs.txt",
+            "monte_carlo_test.outputs.txt",
+        ]:
+            if os.path.exists(filepath):
+                os.remove(filepath)

	with open(f"{output_filename}.csv", "w", newline= "") as f:
	with open(f"{output_filename}.csv", "w", newline="") as f:

-        """Converts the default Monte Carlo .txt output to .cvs or .json file
-        depending on the user's choice
-        Parameters
-        ----------
-        output_filename : str
-            Name of the file in which the converted data will be saved
-        output_format : str
-            Format of the output file
-        Returns
-        -------
-        None
+        """Export Monte Carlo simulation results to CSV or JSON format.
+        This method reads simulation output data from the `.outputs.txt` file
+        (specifically, from `self.filename.outputs.txt`) and converts it to either
+        CSV or JSON format based on user selection. The output file will be
+        overwritten if it already exists.
+        Parameters
+        ----------
+        output_filename : str or Path
+            Path and name of the output file (without extension). The appropriate
+            extension (.csv or .json) will be added automatically.
+        output_format : str
+            Format of the output file. Must be either "csv" or "json"
+            (case-insensitive).
+        Returns
+        -------
+        None
+        Raises
+        ------
+        FileNotFoundError
+            If the `.outputs.txt` file does not exist.
+        ValueError
+            If `output_format` is not "csv" or "json".
+        Examples
+        --------
+        >>> mc.export_results("results", "csv")
+        >>> mc.export_results(Path("results_folder/results"), "json")

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GMinoruy commented Dec 7, 2025

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