How to Install flask in Python?

pip install flask

The Python flask library is among the top 100 Python libraries, with more than 34,481,920 downloads. This article will show you everything you need to get this installed in your Python environment.

How to Install flask on Windows?

  1. Type "cmd" in the search bar and hit Enter to open the command line.
  2. Type “pip install flask” (without quotes) in the command line and hit Enter again. This installs flask for your default Python installation.
  3. The previous command may not work if you have both Python versions 2 and 3 on your computer. In this case, try "pip3 install flask" or “python -m pip install flask“.
  4. Wait for the installation to terminate successfully. It is now installed on your Windows machine.

Here’s how to open the command line on a (German) Windows machine:

Open CMD in Windows

First, try the following command to install flask on your system:

pip install flask

Second, if this leads to an error message, try this command to install flask on your system:

pip3 install flask

Third, if both do not work, use the following long-form command:

python -m pip install flask

The difference between pip and pip3 is that pip3 is an updated version of pip for Python version 3. Depending on what’s first in the PATH variable, pip will refer to your Python 2 or Python 3 installation—and you cannot know which without checking the environment variables. To resolve this uncertainty, you can use pip3, which will always refer to your default Python 3 installation.

How to Install flask on Linux?

You can install flask on Linux in four steps:

  1. Open your Linux terminal or shell
  2. Type “pip install flask” (without quotes), hit Enter.
  3. If it doesn’t work, try "pip3 install flask" or “python -m pip install flask“.
  4. Wait for the installation to terminate successfully.

The package is now installed on your Linux operating system.

How to Install flask on macOS?

Similarly, you can install flask on macOS in four steps:

  1. Open your macOS terminal.
  2. Type “pip install flask” without quotes and hit Enter.
  3. If it doesn’t work, try "pip3 install flask" or “python -m pip install flask“.
  4. Wait for the installation to terminate successfully.

The package is now installed on your macOS.

How to Install flask in PyCharm?

Given a PyCharm project. How to install the flask library in your project within a virtual environment or globally? Here’s a solution that always works:

  • Open File > Settings > Project from the PyCharm menu.
  • Select your current project.
  • Click the Python Interpreter tab within your project tab.
  • Click the small + symbol to add a new library to the project.
  • Now type in the library to be installed, in your example "flask" without quotes, and click Install Package.
  • Wait for the installation to terminate and close all pop-ups.

Here’s the general package installation process as a short animated video—it works analogously for flask if you type in “flask” in the search field instead:

Make sure to select only “flask” because there may be other packages that are not required but also contain the same term (false positives):

How to Install flask in a Jupyter Notebook?

To install any package in a Jupyter notebook, you can prefix the !pip install my_package statement with the exclamation mark "!". This works for the flask library too:

!pip install my_package

This automatically installs the flask library when the cell is first executed.

How to Resolve ModuleNotFoundError: No module named ‘flask’?

Say you try to import the flask package into your Python script without installing it first:

import flask
# ... ModuleNotFoundError: No module named 'flask'

Because you haven’t installed the package, Python raises a ModuleNotFoundError: No module named 'flask'.

To fix the error, install the flask library using “pip install flask” or “pip3 install flask” in your operating system’s shell or terminal first.

See above for the different ways to install flask in your environment.

Improve Your Python Skills

If you want to keep improving your Python skills and learn about new and exciting technologies such as Blockchain development, machine learning, and data science, check out the Finxter free email academy with cheat sheets, regular tutorials, and programming puzzles.

Join us, it’s fun! 🙂