Use `#!/usr/bin/env python3`
#!/usr/bin/python3 only works if python3 is found in /usr/bin. #!/usr/bin/env python3 is more flexible. See e.g. this SO question.
#!/usr/bin/python3 only works if python3 is found in /usr/bin. #!/usr/bin/env python3 is more flexible. See e.g. this SO question.