convert ROS bag to cvs files

bag2csv.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

Usage1 (for one bag file):
	python bag2csv.py filename.bag
Usage 2 (for all bag files in current directory):
	python bag2csv.py

Written by Nick Speal in May 2013 at McGill University's Aerospace Mechatronics Laboratory. Bugfixed by Marc Hanheide June 2016.
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  " + str(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 " + str(numberOfFiles) + " bag files."

I have just taken this gist from the original source and made it work in 2016 for my own purposes. I'm afraid, I don't maintain it, but I welcome anyone taking it and hosting it as a proper project. Also, this one might be a better alternative: https://github.com/AtsushiSakai/rosbag_to_csv

Or simply rostopic echo -b file.bag -p /topic will work for some simple data types. The best is probably the really neat rosbag_pandas package for python that also includes a bag2csv.py tool

Hope this helps @Shivani1796

@marc-hanheide Hi.. Thanks alot for your quick response, but I tried doing it by https://github.com/AtsushiSakai/rosbag_to_csv but was unable to do, could you please help me convert bag file to csv file as I need pose data (rotation & translation matrix) from bag file. Also I am new to this field so it would be great if you could help me solve this problem.

I am new to working with rosbag files and was having a hard time, trying to get rosbag_pandas to work. This script was a lifesaver. Thanks @marc-hanheide