flask print to console

1from __future__ import print_function # In python 2.7
2import sys
3
4@app.route('/button/')
5def button_clicked():
6    print('Hello world!', file=sys.stderr)
7    return redirect('/')

1import sys
2
3print('This is error output', file=sys.stderr)
4print('This is standard output', file=sys.stdout)