from flask import Flask
app = Flask(__name__)
#app.route('/')
def hello_world():
return 'Hello from Flask!'
if __name__ == "__main__":
app.run()
But Python is prompting the following error:
#app.route('/')
...
File "<stdin>", line 2
^
SyntaxError: invalid syntax
I ran your code and it worked for me. There does not seem to be a clear syntax error.
Try saving your file again and clearing your terminal before running it.
Another alternative is running the following in your command prompt before running your code:
set FLASK_APP={name of your file}.py
In the command prompt it should look something like this:
C:\path\to\app>set FLASK_APP=hello.py
Lastly, you can also try running it by writing the following in your command prompt or terminal instead of using the main() function you have now:
python -m flask run
More details and alternatives here: https://flask.palletsprojects.com/en/1.1.x/quickstart/
Hope this helps!
Related
After typing
export FLASK_APP=use_flask.py
And then typing
printenv
which outputs inter alia:
TERM_SESSION_ID=AA805368-CF19-4631-AABB-A0112AD535CE
FLASK_APP=/users/me/documents/pcode/color/use_flask.py
USER=me
CONDA_EXE=/Users/me/Applications/miniconda3/bin/conda
I then place in the file use_flask.py
from flask import Flask
app = Flask(__name__)
#app.route('/')
def hello():
return 'hey man'
And then type
ls
which outputs inter alia
use_flask.py
I then type:
flask run
I get the error
-bash: flask: command not found
I have also tried exporting the full path of the use_flask.py file but that did not work either. What am I doing wrong?
I ran
pip install flask flask-alchemy
I thought I already had flask installed because when I typed
from flask import Flask
into my Pycharm editor and then ran the code no error message occurred. So although I solved the problem I don't understand why it didn't work the first time.
When I try to install anything with Pip, it gives me the "Fatal error in launcher:" error. That wouldn't be too bad, since I know how to update Pip differently. However, the same error occurs when I try to run the "flask run" command.
I'm using Windows 10, Python 3.8.2 and I have previously set the FLASK_APP variable to flaskblog.py. This is its content:
from flask import Flask
app = Flask(__name__)
#app.route("/")
def hello():
return "Hello World!"
Since you haven't posted the error clearly, if Fatal error in launcher: Unable to create process using ‘”‘ is your error,
then you might want to update pip using python -m pip install --upgrade pip and try installing your package again using python -m pip install <pkg-name>. You should get it working.
if the error persists after the above mentioned steps, the try importing pip in your python console(pull up your terminal and type python then type import pip) and try pip.main([‘install’,’<pkg-name>’]) in the console.
Hope this helps.
referred from here
Edit
Alternatively, you can run your flask app by adding app.run() in your script.
Like:
if __name__ == __main__:
app.run()
and then in the terminal, run python -m flaskblog.py.
Note: if you want to run your app in debug mode, consder giving debug = True to app.run().
I am following the tutorial here:
https://blog.miguelgrinberg.com/post/the-flask-mega-tutorial-part-i-hello-world
I have also create a
app/view.py
from app import app
#app.route('/')
#app.route('/index')
def index():
return "Hello World!"
and
app/init.py
from flask import Flask
app = Flask(__name__)
from app import views
I am down to the last step and written the
run.py
file as such:
#!flask/bin/python
from app import app
app.run(debug=True)
I am running it by evoking the ./run.py command in terminal. getting the following error:
from: can't read /var/mail/app
./run.py: line 4: syntax error near unexpected token `debug=True'
./run.py: line 4: `app.run(debug=True)'
I am running a conda virtual environment.
All the answers I see online suggest adding the shebang but its already there. I will appreciate guidance on this.
That's not a valid shebang - it has to be an absolute pathname, in other words the first character after the #! can only be a slash.
Hi All I am just learning about flask. I have used pip to install it. Then when I run this basic code I get an error. Basically I see its working then abruptly exits with the following error. This maybe looks to be some environment issue but I'm not sure. The strange thing this was working the other day now it's not.
from flask import Flask
app = Flask(__name__)
#app.route('/')
def hello_world():
return 'Hello, World!'
if __name__ == '__main__':
app.run(debug=True, port=8000, host='0.0.0.0')
* Running on http://0.0.0.0:8000/ (Press CTRL+C to quit)
* Restarting with stat
/Library/Frameworks/Python.framework/Versions/3.4/bin/python3: can't find '__main__' module in ''
You said, that the problem only occurs when you run the code from an interactive shell. It is caused by a feature in werkzeug (the wsgi server flask is based on).
In debug mode werkzeug will automatically restart your server if a project file is changed. Everytime a change is detected werkzeug restarts the file that was initially started. Even the first start is done via the file name!
But in the interactive shell there is no file at all and werkzeug thinks your file is called "" (empty string). It then tries to run that file. For some reason it also thinks that the "" refers to a package. But since that package does not exist it also cannot have a __main__ module, hence the error.
You can simulate that error by running "" directly
python ""
# prints: can't find '__main__' module in ''
You could try to disabe the reloader by setting debug to False (which is also the default):
app.run(debug=False, ...)
Then it should also run in an interactive session. But why would you do that? Just put in a file and run that.
Let me try to explain my problem with example now.
Here is sample GUI code with Tkinter
from Tkinter import *
root = Tk()
w = Label(root, text="Hello, world!")
w.pack()
root.mainloop()
If I run this code in Ipython, I don't get a command prompt when the GUI is visible.
Now if I comment out the line, "root.mainloop()", the code still works in Ipython and I have access to command prompt so that I can inspect data when the code is running.
Now coming to the Flask case,
from flask import Flask
app = Flask(__name__)
#app.route('/')
def hello_world():
return 'Hello World!'
app.run()
When I run this application in Ipython, I don't get a command prompt. To access variables while the code is running, I need to stop the flask server.
Is there any option to run the flask server and have access to command prompt?
Thank you
I second #NewWorld and would recommend a debugger. You can inspect the program in an IPython shell with the IPython debugger. Install e.g. with:
pip install ipdb
Then load the debugger with: ipdb.set_trace() like;
#app.route('/')
def hello_world():
import ipdb; ipdb.set_trace()
return 'Hello World!'
This will open a IPython command prompt and you can inspect "data while the code is running".
Further information:
Look here to get started with ipdb.
This site gives a short introduction to available commands once inside the debugger.
run the flask application in separate thread.
try this example:-
from flask import Flask
import thread
data = 'foo'
app = Flask(__name__)
#app.route("/")
def main():
return data
def flaskThread():
app.run()
if __name__ == "__main__":
thread.start_new_thread(flaskThread,())
run this file in ipython:-
"run -i filename.py"
then you can access the ipython terminal for inspection.
If you want to use flask shell through ipython you can install the following package:
pip install flask-shell-ipython