How to Set up a Local Python Development Environment

If you are on a Mac or Linux machine, you most likely already have Python installed. Windows users can follow this excellent tutorial. There are more advanced configuration instructions at the official Python website.

Flask is a super web server written in Python. We're going to use it for this tutorial. To install it, we are first going to install two tools: pip and virtualenv.

Many third-party Python libraries, such as the math library numpy, the MySQL connector library MySQL-python, and Flash, are made available as "packages". They are installed using a "package manager". Most Python developers prefer to use a package manager called pip, but easy_install is another.

virtualenv is a tool that lets you create a special sandbox for each of your Python projects, to ensure that you have exactly the right version of every tool you need for that particular project. Furthermore, virtualenv makes sure that you don't accidentally break your app if someone updates your Python packages.

We first need to make sure that we install pip and virtualenv for the correct version of Python on your computer. Open a terminal and run the following command:

python --version

It should say something like the following:

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python --version
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Python 3.9.1

Find the instructions below to install virtualenv for the version of Python reported by your terminal.

Run the following command:

easy_install virtualenv

If your Python version is 2.5, 2.6 or 2.7, run easy_install with your Python version number, like this:

easy_install-2.7 virtualenv

Replace the version number 2.7 above with 2.5 or 2.6 if you have that version installed.

pip is included in Python 3.4+ installations, so just install virtualenv with:

pip install virtualenv

If you get any permission denied errors, try running sudo python instead of python.

If you get an easy_install-2.5: command not found error, you may need to check that Python is installed or add the folder containing the easy_install program to your $PATH.

If you get an error that looks like this:

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Installing pip script to /usr/local/bin
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error: /usr/local/bin/pip: Permission denied

Then you need to run the install script as the admin user, like this:

sudo easy_install-2.6 virtualenv

Once you have virtualenv installed, switch to the directory you'll use for your tutorial, and create a virtual environment:

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cd Documents/my_tutorial_folder
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virtualenv --no-site-packages .

Now activate the virtual environment.

source bin/activate

On Windows, use .\bin\activate.bat.

You can tell your virtual environment is running because your terminal will have the name of the enclosing folder listed above it:

(quickstart)USER:~ user$

Now we're going to install Flask and the twilio-python library. Create a file called requirements.txt and add the following lines to it:

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Flask>=0.12
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twilio~=6.0.0

Install these packages with pip:

bin/pip install -r requirements.txt

Create a file called run.py and add these lines to it:

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from flask import Flask
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app = Flask(__name__)
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@app.route("/")
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def hello():
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  return "Hello World!"
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if __name__ == "__main__":
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  app.run(debug=True)

Now run it. In your terminal, type:

python run.py

You should see the output:

* Running on http://127.0.0.1:5000/ 

Navigate to http://localhost:5000 in a browser. You should see a "Hello World" message.

You now have everything you need to start using Twilio and Python! Let's start coding.