
A requirements.txt file is mostly used in virtual environments. Virtual
environments provide a way to keep project dependencies isolated from other
installed packages on a system and reduce errors when transferring the
project to another location like another computer.

Many packages are updated regularly and oftentimes an issue can occur when a
package is updated within a project. A project could break entirely during
one of theses routine updates. You could also have the latest version of a package
and when someone tries to run the application With an older version, they will likely
come into some problems. With a requirements.txt file you have more
control over versions of installed packages. Now, whenever anyone else uses
the projects they will have the same dependencies as you.

Assuming you have PIP installed, run the following command to check what
packages you have installed. Your virtual environment should be running
before you enter this command.

```python
pip freeze
```

You may need to run python -m if the above command does not work. If that
doesn't work then you likely do not have pip installed.

```python
python -m pip freeze
```

Here is what it might look like.

<Image src="/images/python1.png" />

You can save this output to a requirements.txt like so

```python
pip freeze > requirements.txt
```

You should now have a requirements.txt file in your current working
directory with a list of installed packages. Now, when transferring your
project you can simply send only your requirements.txt file instead of your
entire virtual environment folder that has all the installed packages. If
you were to download a repository from Github with a requirements.txt file
you can easily install all the packages and their versions.

```python
pip install -r requirements.txt
```

<Image src="/images/python2.png" size="10rem" />

I hope this short guide helped your understanding of what a requirements.txt
file is and when and how it can be useful.


GoganWare

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What is a requirements.txt file?