Script to extract messages on desired topics, and save them in a CSV file. Easy to modify as per requirements.

rosbag_extract.py

"""
This script collects data from all the bag files in the directory passed as the first
argument when launching. In particular, it collects the rostopics listed in the
concerned list and generates a CSV file containing the same. The readings are triggered
by the trigger topic.

Author: Dhruv Ilesh Shah
[email protected] | [email protected]
"""

import rosbag
import numpy as np
import sys, os
import csv
import yaml

rostopics = ["/polaris_h_rad", "/lilred_velocity_controller/odom"]
trigger = 0  # This stores the index of the trigger topic. Here, /polaris_h_rad

print(chr(27) + "[2J")
print "Entering", sys.argv[1]

for filename in os.listdir(sys.argv[1]):
    print "Opening", filename
    bag = rosbag.Bag(os.path.join(sys.argv[1], filename))
    bag_info = yaml.load(bag._get_yaml_info())
    print "Found bag with duration", bag_info['duration'], "seconds"
    print "Parsing", filename

    csv_file = filename + ".csv"
    csvfile = open(csv_file, 'wb')
    writer = csv.writer(csvfile, delimiter=',')
    flag = 0
    row = []

    for msg in bag.read_messages(topics=rostopics):
        if msg[0] == rostopics[trigger]:
            # Trigger found. Get ready to accept other topics
            flag = 1
            row = []
            # print "- - - - - - - - - - - - - - - - - - - - - - - -"
        if flag:
            if msg[0] in rostopics:
                if msg[0] == "/polaris_h_rad":
                    # print "Rad: ", msg[1].multi_array.layout.dim[0].size
                    row.append(msg[1].multi_array.layout.dim[0].size)
                elif msg[0] == "/lilred_velocity_controller/odom":
                    # print "Odom: ", msg[1].pose.pose.position
                    row.extend([msg[1].pose.pose.position.x, msg[
                               1].pose.pose.position.y, msg[1].pose.pose.position.z])
                    flag = 0
                    writer.writerow(row)
    print "Parsed data. Saved as", csv_file

rosbag_to_csv_general.py

'''
This script saves each topic in a bagfile as a csv.

Accepts a filename as an optional argument. Operates on all bagfiles in current directory if no argument provided

Written by Nick Speal in May 2013 at McGill University's Aerospace Mechatronics Laboratory
www.speal.ca

Supervised by Professor Inna Sharf, Professor Meyer Nahon 

'''

import rosbag, sys, csv
import time
import string
import os #for file management make directory
import shutil #for file management, copy file

#verify correct input arguments: 1 or 2
if (len(sys.argv) > 2):
	print "invalid number of arguments:   " + str(len(sys.argv))
	print "should be 2: 'bag2csv.py' and 'bagName'"
	print "or just 1  : 'bag2csv.py'"
	sys.exit(1)
elif (len(sys.argv) == 2):
	listOfBagFiles = [sys.argv[1]]
	numberOfFiles = "1"
	print "reading only 1 bagfile: " + str(listOfBagFiles[0])
elif (len(sys.argv) == 1):
	listOfBagFiles = [f for f in os.listdir(".") if f[-4:] == ".bag"]	#get list of only bag files in current dir.
	numberOfFiles = str(len(listOfBagFiles))
	print "reading all " + numberOfFiles + " bagfiles in current directory: \n"
	for f in listOfBagFiles:
		print f
	print "\n press ctrl+c in the next 10 seconds to cancel \n"
	time.sleep(10)
else:
	print "bad argument(s): " + str(sys.argv)	#shouldnt really come up
	sys.exit(1)

count = 0
for bagFile in listOfBagFiles:
	count += 1
	print "reading file " + str(count) + " of  " + numberOfFiles + ": " + bagFile
	#access bag
	bag = rosbag.Bag(bagFile)
	bagContents = bag.read_messages()
	bagName = bag.filename


	#create a new directory
	folder = string.rstrip(bagName, ".bag")
	try:	#else already exists
		os.makedirs(folder)
	except:
		pass
	shutil.copyfile(bagName, folder + '/' + bagName)


	#get list of topics from the bag
	listOfTopics = []
	for topic, msg, t in bagContents:
		if topic not in listOfTopics:
			listOfTopics.append(topic)


	for topicName in listOfTopics:
		#Create a new CSV file for each topic
		filename = folder + '/' + string.replace(topicName, '/', '_slash_') + '.csv'
		with open(filename, 'w+') as csvfile:
			filewriter = csv.writer(csvfile, delimiter = ',')
			firstIteration = True	#allows header row
			for subtopic, msg, t in bag.read_messages(topicName):	# for each instant in time that has data for topicName
				#parse data from this instant, which is of the form of multiple lines of "Name: value\n"
				#	- put it in the form of a list of 2-element lists
				msgString = str(msg)
				msgList = string.split(msgString, '\n')
				instantaneousListOfData = []
				for nameValuePair in msgList:
					splitPair = string.split(nameValuePair, ':')
					for i in range(len(splitPair)):	#should be 0 to 1
						splitPair[i] = string.strip(splitPair[i])
					instantaneousListOfData.append(splitPair)
				#write the first row from the first element of each pair
				if firstIteration:	# header
					headers = ["rosbagTimestamp"]	#first column header
					for pair in instantaneousListOfData:
						headers.append(pair[0])
					filewriter.writerow(headers)
					firstIteration = False
				# write the value from each pair to the file
				values = [str(t)]	#first column will have rosbag timestamp
				for pair in instantaneousListOfData:
					if len(pair) > 1:
						values.append(pair[1])
				filewriter.writerow(values)
	bag.close()
print "Done reading all " + numberOfFiles + " bag files."