import rosbag
bag = rosbag.Bag('test.bag')
for topic, msg, t in bag.read_messages(topics=['chatter', 'numbers']):
    print(msg)
bag.close()

import classic_bags
bag = classic_bags.Bag('test.bag')
for topic, msg, t in bag.read_messages(topics=['chatter', 'numbers']):
    print(msg)
# bag.close() Closing bag is not necessary

import rosbag
from std_msgs.msg import Int32, String

bag = rosbag.Bag('test.bag', 'w')

try:
    s = String()
    s.data = 'foo'

    i = Int32()
    i.data = 42

    bag.write('chatter', s)
    bag.write('numbers', i)
finally:
    bag.close()

import classic_bags
from std_msgs.msg import Int32, String

bag = classic_bags.Bag('test.bag', 'w')

try:
    s = String()
    s.data = 'foo'

    i = Int32()
    i.data = 42

    bag.write('chatter', s)
    bag.write('numbers', i)
finally:
    bag.close()  # Closing is not strictly necessary

import classic_bags
from std_msgs.msg import String
import rclpy.time
import builtin_interfaces.msg


with classic_bags.Bag('test.bag', 'w') as bag:
    s = String()
    s.data = 'foo'

    # The third argument of the write method is the timestamp

    # Floats are interpreted as seconds since epoch
    bag.write('chatter', s, 456606000.5)

    # Ints are interpreted as nanoseconds since epoch
    bag.write('chatter', s, 456606000600000000)

    # You can also use rclpy.time.Time
    pytime = rclpy.time.Time(seconds=456606000, nanoseconds=700000000)
    bag.write('chatter', s, pytime)

    # Or a timestamp from a message
    msgtime = builtin_interfaces.msg.Time()
    msgtime.sec = 456606000
    msgtime.nanosec = 800000000
    bag.write('chatter', s, msgtime)

    # If none is specified, the system time will be used
    bag.write('chatter', s)