Flask: "OSError: [Errno 8] Exec format error" when execute bit is set

Created on 7 May 2019 · 4Comments · Source: pallets/flask

Expected Behavior

Place the following code into main.py.

from flask import Flask


app = Flask(__name__)
app.config['DEBUG'] = True

@app.route('/')
def root():
    return ":)"

app.run()

Set the execute bit on main.py:
chmod +x main.py
Running the following command should start the server: python main.py

Actual Behavior

$ python main.py
 * Serving Flask app "main" (lazy loading)
 * Environment: production
   WARNING: Do not use the development server in a production environment.
   Use a production WSGI server instead.
 * Debug mode: on
 * Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)
 * Restarting with stat
Traceback (most recent call last):
  File "main.py", line 11, in <module>
    app.run()
  File "/Users/wadegilmer/miniconda3/envs/hello-flask/lib/python3.7/site-packages/flask/app.py", line 943, in run
    run_simple(host, port, self, **options)
  File "/Users/wadegilmer/miniconda3/envs/hello-flask/lib/python3.7/site-packages/werkzeug/serving.py", line 988, in run_simple
    run_with_reloader(inner, extra_files, reloader_interval, reloader_type)
  File "/Users/wadegilmer/miniconda3/envs/hello-flask/lib/python3.7/site-packages/werkzeug/_reloader.py", line 332, in run_with_reloader
    sys.exit(reloader.restart_with_reloader())
  File "/Users/wadegilmer/miniconda3/envs/hello-flask/lib/python3.7/site-packages/werkzeug/_reloader.py", line 176, in restart_with_reloader
    exit_code = subprocess.call(args, env=new_environ, close_fds=False)
  File "/Users/wadegilmer/miniconda3/envs/hello-flask/lib/python3.7/subprocess.py", line 323, in call
    with Popen(*popenargs, **kwargs) as p:
  File "/Users/wadegilmer/miniconda3/envs/hello-flask/lib/python3.7/subprocess.py", line 775, in __init__
    restore_signals, start_new_session)
  File "/Users/wadegilmer/miniconda3/envs/hello-flask/lib/python3.7/subprocess.py", line 1522, in _execute_child
    raise child_exception_type(errno_num, err_msg, err_filename)
OSError: [Errno 8] Exec format error: '/Users/wadegilmer/lc101/flask_error/main.py'

Environment

osx version: 10.13.6
Python version: 3.7.3
Flask version: 1.0.2
Werkzeug version: 0.15.2

Commentary

Adding a shabang line to main.py resolves the issue but is kind of unexpected. Additionally removing the execute bit also resolves the issue. Is this the expected behavior?

Source

wadegilmer

Most helpful comment

Duplicate of https://github.com/pallets/werkzeug/issues/1482. You've marked a script as executable but didn't add an interpreter comment at the top. Either add #! /usr/bin/env python or unset the executable bit. Or use the recommended flask run command to run the development server.