rospy.loginfo is not printing when node is started with a launch file

edit

I did the very helpfull beginner tutorials and wanted to apply what I learned on a self written example. Therefore I wrote a package called "calculate" with a "calc_talker" node that calculates the fibonacci numbers and a "calc_listener" node that listens to them.

calc_talker:

#!/usr/bin/env python

import rospy
from calculate.msg import Calc

def talker():
    pub = rospy.Publisher("Calc_Chatter", Calc, queue_size=100)
    rospy.init_node("Calc_Talker", anonymous=True)
    rate = rospy.Rate(10)

    count   = 3
    number1 = 1
    number2 = 1

    while not rospy.is_shutdown():

        result = number1 + number2

        msg = Calc()
        msg.first_number = number1
        msg.second_number = number2
        msg.result = f"The {count} fibonacci number is {result}"

        number2 = number1
        number1 = result
        count = count + 1

        rospy.loginfo(msg)
        pub.publish(msg)
        rate.sleep()


if __name__ == "__main__":
    try:
        talker()
    except rospy.ROSInterruptException:
        pass
#EoF

calc_listener:

#!/usr/bin/env python

import rospy
from calculate.msg import Calc

def callback(data):
    msg = f"{data.result}. It was calculated from {data.first_number} and {data.second_number}"
    rospy.loginfo(msg)


def listener():
    rospy.init_node("Calc_Listener", anonymous=True)
    rospy.Subscriber("Calc_Chatter", Calc, callback)
      rospy.spin()


if __name__ == "__main__":
    listener()
#EoF

When i start the nodes with rosrun i get the following example output:

rosrun calculate calc_talker.py:

[INFO] [1612869970.095087]: first_number: 1 second_number 1 result: "The 3 fibonacci number is 2"

rosrun calculate calc_listener.py:

[INFO] [1612869970]: The 3 fibonacci number is 2. It was calculated from 1.0 and 1.0

I wrote a simple launch file to launch both nodes:

<launch>

    <group ns="talker">
        <node pkg="calculate" name="my_calc_talker" type="calc_talker.py"/>
    </group>

    <group ns="listener">
        <node pkg="calculate" name="my_calc_listener" type="calc_listener.py" output="screen"/>
    </group>

</launch>

My Problem: When i add output="screen" to the calc_talker i get the expected log output. However i does not work when i add it to the calc_listener and i can not find out why. I am very grateful for your help!