Add module to extract message values for use in scripting

pyulog/extract_message.py

@@ -0,0 +1,53 @@
+"""
+Extract values from a ULog file message to use in scripting
+"""
+
+import numpy as np
+from .core import ULog
+
+def extract_message(ulog_file_name: str, message: str, time_s: "int | None" = None, time_e: "int | None" = None,
+                     disable_str_exceptions=False) -> list[dict]:
+    """
+    Extract values from a ULog file
+
+    :param ulog_file_name: (str) The ULog filename to open and read
+    :param message: (str) A ULog message to return values from
+    :param time_s: (int) Offset time for conversion in seconds
+    :param time_e: (int) Limit until time for conversion in seconds
+
+    :return: (list[dict]) A list of each record from the ULog as key-value pairs
+    """
+
+    if not type(message) == str:
+        raise AttributeError("Must provide a message to pull from ULog file")
+
+    msg_filter = message.split(',') if message else None
+
+    ulog = ULog(ulog_file_name, msg_filter, disable_str_exceptions)
+    data = ulog.data_list
+
+    if not data:
+        raise AttributeError("Provided message is not in the ULog file")
+
+    values = []
+    for record in data:
+        # use same field order as in the log, except for the timestamp
+        data_keys = [f.field_name for f in record.field_data]
+        data_keys.remove('timestamp')
+        data_keys.insert(0, 'timestamp')  # we want timestamp at first position
+
+        #get the index for row where timestamp exceeds or equals the required value
+        time_s_i = np.where(record.data['timestamp'] >= time_s * 1e6)[0][0] \
+                if time_s else 0
+        #get the index for row upto the timestamp of the required value
+        time_e_i = np.where(record.data['timestamp'] >= time_e * 1e6)[0][0] \
+                if time_e else len(record.data['timestamp'])
+
+        # write the data
+        for i in range(time_s_i, time_e_i):
+            row = {}
+            for k in range(len(data_keys)):
+                row[data_keys[k]] = record.data[data_keys[k]][i]
+            values.append(row)
+
+    return values