ENH: Add custom JSON encoder for RocketPy objects

- This improves the file saving/reading methods
- Sorry for implementing a new feature in this PR, it it feels like the right thing to do right now. I'm running late sorry.

rocketpy/_encoders.py

@@ -0,0 +1,43 @@
+"""Defines a custom JSON encoder for RocketPy objects."""
+
+import json
+import types
+
+import numpy as np
+
+from rocketpy.mathutils.function import Function
+
+
+class RocketPyEncoder(json.JSONEncoder):
+    """NOTE: This is still under construction, please don't use it yet."""
+
+    def default(self, o):
+        if isinstance(
+            o,
+            (
+                np.int_,
+                np.intc,
+                np.intp,
+                np.int8,
+                np.int16,
+                np.int32,
+                np.int64,
+                np.uint8,
+                np.uint16,
+                np.uint32,
+                np.uint64,
+            ),
+        ):
+            return int(o)
+        elif isinstance(o, (np.float_, np.float16, np.float32, np.float64)):
+            return float(o)
+        elif isinstance(o, np.ndarray):
+            return o.tolist()
+        elif hasattr(o, "to_dict"):
+            return o.to_dict()
+        # elif isinstance(o, Function):
+        #     return o.__dict__()
+        elif isinstance(o, (Function, types.FunctionType)):
+            return repr(o)
+        else:
+            return json.JSONEncoder.default(self, o)

rocketpy/simulation/monte_carlo.py

@@ -6,6 +6,7 @@
 import numpy as np
 import simplekml
 
+from rocketpy._encoders import RocketPyEncoder
 from rocketpy.plots.monte_carlo_plots import _MonteCarloPlots
 from rocketpy.prints.monte_carlo_prints import _MonteCarloPrints
 from rocketpy.simulation.flight import Flight
@@ -260,8 +261,9 @@ def __export_flight_data(
         }
 
         # Write flight setting and results to file
-        input_file.write(f"{inputs_dict}\n")
-        output_file.write(f"{results}\n")
+        # TODO: use json.dumps (requires custom JSONEncoder child class)
+        input_file.write(f"{json.dumps(inputs_dict, cls=RocketPyEncoder)}\n")
+        output_file.write(f"{json.dumps(results, cls=RocketPyEncoder)}\n")
 
     def __check_export_list(self, export_list):
         """Checks if the export_list is valid and returns a valid list. If no
@@ -421,80 +423,29 @@ def error_file(self, value):
     # setters for post simulation attributes
     def set_inputs_log(self):
         """Sets inputs_log from a file into an attribute for easy access"""
-        # TODO: add pickle package to deal with parachute triggers and Function objects
         self.inputs_log = []
-        with open(self.input_file, mode="r", encoding="utf-8") as inputs:
-            # Loop through each line in the file
-            for line in inputs:
-                # swap "<" and ">" to "'"
-                # this is done to interpret the trigger functions
-                # Find the index of the first and last occurrences of '<' and '>'
-                first_lt_index = line.find("<")
-                last_gt_index = line.rfind(">")
-                if first_lt_index != -1 and last_gt_index != -1:
-                    # Replace the first '<' and last '>' with double quotes
-                    line = (
-                        line[:first_lt_index]
-                        + '"'
-                        + line[first_lt_index + 1 : last_gt_index]
-                        + '"'
-                        + line[last_gt_index + 1 :]
-                    )
-
-                # # Skip comments lines
-                if line[0] != "{":
-                    continue
-                # Try to convert the line to a dictionary
-                try:
-                    d = json.loads(line)
-                    # If successful, append the dictionary to the list
-                    self.inputs_log.append(d)
-                except json.JSONDecodeError:
-                    continue
+        with open(self.input_file, mode="r", encoding="utf-8") as rows:
+            for line in rows:
+                self.inputs_log.append(json.loads(line))
 
     def set_outputs_log(self):
         """Sets outputs_log from a file into an attribute for easy access"""
         self.outputs_log = []
-        # Loop through each line in the file
-        with open(self.output_file, mode="r", encoding="utf-8") as outputs:
-            for line in outputs:
-                # Skip comments lines
-                if line[0] != "{":
-                    continue
-                # Try to convert the line to a dictionary
-                try:
-                    # If successful, append the dictionary to the list
-                    self.outputs_log.append(json.loads(line))
-                except json.JSONDecodeError:
-                    continue
+        with open(self.output_file, mode="r", encoding="utf-8") as rows:
+            for line in rows:
+                self.outputs_log.append(json.loads(line))
 
     def set_errors_log(self):
         """Sets errors_log log from a file into an attribute for easy access"""
         self.errors_log = []
-        # Loop through each line in the file
         with open(self.error_file, mode="r", encoding="utf-8") as errors:
             for line in errors:
-                # Skip comments lines
-                if line[0] != "{":
-                    continue
-                # Try to convert the line to a dictionary
-                try:
-                    # If successful, append the dictionary to the list
-                    self.errors_log.append(json.loads(line))
-                except json.JSONDecodeError:
-                    continue
+                self.errors_log.append(json.loads(line))
 
     def set_num_of_loaded_sims(self):
         """Number of simulations loaded from output_file being currently used."""
-        # Calculate the number of flights simulated
-        self.num_of_loaded_sims = 0
-        # Loop through each line in the file
         with open(self.output_file, mode="r", encoding="utf-8") as outputs:
-            for line in outputs:
-                # Skip comments lines
-                if line[0] != "{":
-                    continue
-                self.num_of_loaded_sims += 1
+            self.num_of_loaded_sims = sum(1 for _ in outputs)
 
     def set_results(self):
         """Monte carlo results organized in a dictionary where the keys are the
@@ -531,25 +482,19 @@ def import_outputs(self, filename=None):
         -------
         None
         """
-        # select file to use
         filepath = filename if filename else self.filename
 
         try:
             with open(f"{filepath}.outputs.txt", "r+", encoding="utf-8"):
                 self.output_file = f"{filepath}.outputs.txt"
-                # Print the number of flights simulated
-                print(
-                    f"A total of {self.num_of_loaded_sims} simulations results were loaded from"
-                    f" the following output file: {filepath}.outputs.txt\n"
-                )
         except FileNotFoundError:
             with open(filepath, "r+", encoding="utf-8"):
                 self.output_file = filepath
-                # Print the number of flights simulated
-                print(
-                    f"A total of {self.num_of_loaded_sims} simulations results were loaded from"
-                    f" the following output file: {filepath}\n"
-                )
+
+        print(
+            f"A total of {self.num_of_loaded_sims} simulations results were "
+            f"loaded from the following output file: {self.output_file}\n"
+        )
 
     def import_inputs(self, filename=None):
         """Import monte carlo results from .txt file and save it into a
@@ -565,19 +510,16 @@ def import_inputs(self, filename=None):
         -------
         None
         """
-        # select file to use
         filepath = filename if filename else self.filename
 
         try:
             with open(f"{filepath}.inputs.txt", "r+", encoding="utf-8"):
                 self.input_file = f"{filepath}.inputs.txt"
-                # Print the number of flights simulated
-                print(f"The following input file was imported: {filepath}.inputs.txt\n")
         except FileNotFoundError:
             with open(filepath, "r+", encoding="utf-8"):
                 self.input_file = filepath
-                # Print the number of flights simulated
-                print(f"The following input file was imported: {filepath}\n")
+
+        print(f"The following input file was imported: {self.input_file}\n")
 
     def import_errors(self, filename=None):
         """Import monte carlo results from .txt file and save it into a
@@ -593,19 +535,15 @@ def import_errors(self, filename=None):
         -------
         None
         """
-        # select file to use
         filepath = filename if filename else self.filename
 
         try:
             with open(f"{filepath}.errors.txt", "r+", encoding="utf-8"):
                 self.error_file = f"{filepath}.errors.txt"
-                # Print the number of flights simulated
-                print(f"The following error file was imported: {filepath}.errors.txt\n")
         except FileNotFoundError:
             with open(filepath, "r+", encoding="utf-8"):
                 self.error_file = filepath
-                # Print the number of flights simulated
-                print(f"The following error file was imported: {filepath}\n")
+        print(f"The following error file was imported: {self.error_file}\n")
 
     def import_results(self, filename=None):
         """Import monte carlo results from .txt file and save it into a