Running Python3 on the ubuntu 18.04 virtual machine terminal without using "python3"

I am trying to run a python program on the terminal directly without using the interpreter's name but I am getting error:

$ cat > scr.py
 #!/usr/bin/env python3
 
 print ("Hello World") ^Z [2]+  Stopped                 cat > scr.py

But when I try to execute the program:

osboxes@osboxes:~$ ./scr.py
bash: ./scr.py: /usr/bin/env: bad interpreter: Text file busy
osboxes@osboxes:~$ chmod +x scr.py
osboxes@osboxes:~$ ./scr.py
bash: ./scr.py: /usr/bin/env: bad interpreter: Text file busy
osboxes@osboxes:

But when I use the name "python3" explicitly, the program executes

osboxes@osboxes:~$ cat scr.py
#!/usr/bin/env python3

print ("Hello World")
osboxes@osboxes:~$ python3 scr.py
Hello World
osboxes@osboxes:~$ 
 

Somebody please guide me how to solve this problem.

Zulfi.