Cannot run node with rosrun but only python

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Hello,

I have an arm based system, with ubuntu 18.04 running melodic. I have a sample code to run a node that only publishes an array defied in a custom message:

 import rospy
from dma.msg import dma_data

def dma_loop():
    pub = rospy.Publisher('DMA_output', dma_data, queue_size=10)
    rospy.init_node('talker', anonymous=True)
    rate = rospy.Rate(2) # 10hz
    vec = dma_data()
    num = 0
    while not rospy.is_shutdown():
        #hello_str = "hello world %s" % rospy.get_time()
        #rospy.loginfo(hello_str)
        #pub.publish(hello_str)
        num = num + 1
        if num>251:
            num=0
        vec.array = [num, num, num, num, num]
        #for i in range(5):
        #    vec.array[i] = num
        pub.publish(vec)
        rate.sleep()

if __name__ == '__main__':
    try:
        dma_loop()
    except rospy.ROSInterruptException:
        pass

After running catkin_make and sourcing devel/setup.bash if I run rosrun, I get:

xilinx@pynq:~$ rosrun dma loop.py 
/home/xilinx/catkin_ws/src/dma/scripts/loop.py: line 1: import: command not found
from: can't read /var/mail/dma.msg
/home/xilinx/catkin_ws/src/dma/scripts/loop.py: line 4: syntax error near unexpected token `('
/home/xilinx/catkin_ws/src/dma/scripts/loop.py: line 4: `def dma_loop():'

However, if I execute it directly with python it works and I can echo the topic that it publishes. Is there something else to do?

Thank you.