execute hello world with flask "ImportError: No module named flask"

Question

I'm trying to use flask and python. I did a simple file named hello.py. tHis file contains this code:

from flask import Flask
app = Flask(__name__)


@app.route("/")
def main():
    return "Welcome!"

if __name__ == "__main__":
    app.run()

This is a simple hello world with flask. I want to execute it but actually, I have a problem. In the terminal, I typed python hello.py and I get this error:

File "hello.py", line 1, in <module>
from flask import Flask
ImportError: No module named flask

Even that I installed flask globally. I understand that this is a basic question, but I'm stuck?

If you are on windows : py -2 -m pip install flask (for python3 use -3) — Yoav Glazner, Jan 14 '16 at 09:26
Had this before, have you got more than one instance of python running? Sometimes Flask installs in 3 for example but the terminal/command line is in 2 etc — Daniel Casserly, Jan 14 '16 at 10:12
Please run `python -m pip list`? Is Flask listed? If not, run `python -m pip install flask`. — dirn, Jan 14 '16 at 12:44

Tomasz Jakub Rup · Answer 1 · 2016-01-14T10:18:25.320

23

You don't have installed flask

Linux:

Install flask as global package:

sudo pip install flask

Install in virtualenv

virtualenv venv
source venv
pip install flask

Install system package

debian, ubuntu
```
apt-get install python-flask
```
arch
```
pacman -S python-flask
```
fedora
```
yum install python-flask
```

Install via Anaconda

conda install flask

Windows:

python -m pip install flask

edited Jan 14 '16 at 10:18

answered Jan 14 '16 at 09:44

Tomasz Jakub Rup

10,502
7
48
49

I'm not sure since OP said: *Even that I installed flask globally. I understand that this is a basic question, but I'm stuck?* – Remi Guan Jan 14 '16 at 09:46
By the way, there's also some Red Hat, Fedora Linux. – Remi Guan Jan 14 '16 at 09:47
@KevinGuan Run console / terminal and type: `python -V` and next type `pip list` – Tomasz Jakub Rup Jan 14 '16 at 11:08

score 1 · Answer 2 · answered Apr 30 '20 at 07:33

1

You've installed flask for python2 you need to use sudo pip3 install ... to get it for python3. I had spent a day when I got that I was using pip for python 2.

answered Apr 30 '20 at 07:33

Ata

33
1
11

score 0 · Answer 3 · answered Nov 28 '20 at 01:21

0

You have to install flask with pip install flask

answered Nov 28 '20 at 01:21

Noah -

33
7

score 0 · Answer 4 · answered May 12 '21 at 15:46

0

Make sure that you entered the correct entry into the requirements.txt file. It should not be blank.

enter Flask==2.0.0 into the requirements.txt file.

answered May 12 '21 at 15:46

Snehasish Chowdhury

1

1

Rather than editing the requirements.txt file manually, it should be auto-generated it so that you are sure it matches your current environment. See [Automatically create requirements.txt](https://stackoverflow.com/questions/31684375/automatically-create-requirements-txt) – Gino Mempin May 12 '21 at 23:37
It was nice to know that it could be generated automatically. – Snehasish Chowdhury May 14 '21 at 02:00

score 0 · Answer 5 · answered Jun 18 '21 at 12:33

Try to install flask package globally using the following command,

pip install flask

Still you are having the same error then you have more than one version of python installed in your machine. So better to create a virtual environment for your app and install all package in it. For that install virtual environment.

py -m pip install --user virtualenv

Activate your venv by

.\venv\Scripts\activate.bat

Now try to install flask in the venv

python -m virtualenv venv

score 0 · Answer 6 · answered Dec 13 '22 at 22:51

0

if you install the flask and still get the error. Then, You should activate the source by following:

source env/bin/activate

answered Dec 13 '22 at 22:51

Borhan

1
1

1

This solution is already provided in another answer. If you have any different solution please mention it. If there is any change/extension required to the original answer, then edit it. – Azhar Khan Dec 17 '22 at 08:11

execute hello world with flask "ImportError: No module named flask"

6 Answers6

Linux:

Windows: