Lame-Ov2.0 Lame-Ov2.0 - 3 months ago 23
Python Question

Python script: problems with shebang line (unix)

I am trying to get a feel for the Flask microframework by launching a test application to local server. When trying to run my code,

app.py
, I keep getting the error message:

-bash: ./app.py: /flask/bin/python: bad interpreter: No such file or directory


Here is the basic code (taken from here) for
app.py
, which lives in my todo-api directory:

#!/flask/bin/python
from flask import Flask

app = Flask(__name__)

@app.route('/')
def index():
return "Hello, World!"

if __name__ == '__main__':
app.run(debug=True)


I've checked the file path to the python interpreter, and it should exist:

:bin $ pwd python

Users/me/Documents/Python/todo-api/flask/bin


I have followed the tutorial to the T; I've tried changing the shebang line to:

#!/flask/bin/python2.x
#!flask/bin/python
#!/flask/bin/env python


But to no avail. I am not that knowledgeable about bash, and have tried looking up what is going on, but the solutions to folks with similar problems have not worked for me; is there something going on behind the scenes that I am not understanding?

Answer

Bash shebangs expect an absolute path to the interpreter. So in your case you need to specify the full path to your Python interpreter i.e.:

#!/Users/me/Documents/Python/todo-api/flask/bin

You might want to investigate the use of /usr/bin/env python to be able to use the interpreter that is available in your user's $PATH environment variable. See http://unix.stackexchange.com/questions/12736/how-does-usr-bin-env-know-which-program-to-use/12751#12751

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