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11.2. Dependency management in Python

There are various dependency management tools available in python. some of them are pip, conda, poetry, etc. pip comes by default with python and is used as the default package manager by majority of developers and companies while conda is popular among data scientists with little exposure in software development.

The pip package manager

  • It is a python package manager that comes along with python.
  • It is also known as Dependency Management system
  • It is going to install/ uninstall specific version of softwares to your environment.
  • example: PIP conda

In this session, we're going to use PIP PIP comes along with python. PIP is the standard or default package manager for python.

checking if pip is installed

If it is installed, it would show you the version number along with the path of the executable

$ pip --version

pip 21.3.1 from C:\Users\user\AppData\Local\Programs\Python\Python39\lib\site-packages\pip (python 3.9)

in some linux OS, you might need to use pip3 instead of pip

If the pip is not installed, we would see the error message. If you're using windows and you installed python, it automatically installs pip by default

$ pip --version

Command 'pip' not found, but can be installed with:

sudo apt install python3-pip

Installing new packages

  • We use pip install [package_name] to install the package to our existing environment.
  • Sometimes we want to install specific version of the package, in that case we use pip install [package_name]==[version_name]
  • To install the packages in range, we can use symbols such as ==, <=, >=, ~=, etc.
  • We can even use Wildcards (eg: 1.2.* ) to install packages

The following are examples to install django with pip:

$ pip install django    # installs the latest release

$ pip install Django==3.2.12  # installs the specific release

$ pip install Django~=3.2   # installs the latest patch of the equivalent django release

$ pip install Django>=3.2  # installs the optimum version of djano greater than 3.2

$ pip install Django<3.3  # installs the most recent version of django less than 3.3

$ pip install Django==3.2.* # installs the latest patch release of django 3.2

Checking the list of installed packages

We can use pip list or pip freeze commands to list out the installed packages.

pip list

$ pip list

Package                      Version
---------------------------- ---------
absl-py                      1.0.0
anyio                        3.5.0
argon2-cffi                  21.3.0
argon2-cffi-bindings         21.2.0
asgiref                      3.4.1
Django                       3.2.12

pip freeze

$ pip freeze

absl-py==1.0.0
anyio==3.5.0
argon2-cffi==21.3.0
argon2-cffi-bindings==21.2.0
asgiref==3.4.1
Django==3.2.12

we can export current installed packages to the requirements.txt file so that we can install the same version of packages in the future.

Exporting the list of packages with pip freeze

sometimes we install so many packages so that we can not remember the packages and their versions while installing, so we want to store them in a special files called requirements.txt. We can use any filename but requirements.txt is the standard and the syntax is highlighted by different IDEs and code editors.

$ pip freeze > requirements.txt

The above command saves all the requirements to the file requirements.txt from the current environment.

absl-py==1.0.0
anyio==3.5.0
argon2-cffi==21.3.0
argon2-cffi-bindings==21.2.0
asgiref==3.4.1
Django==3.2.12

Installing packages from requirements.txt

We can install packages from the requirements file using the command pip install -r [path/to/the/requirements.txt]

$ pip install -r requirements.txt

Upgrading the previously installed package

If we want to upgrade the current version of packages then we can install the newer version with the following methods:

  • pip install [package]==[new_version_number] command with the specific release version
  • pip install -U [package] command.

When we try to run above commands, the older versions gets uninstalled and the newer version gets installed.

Suppose we have installed django of version 3.2.10, and want to install the latest one, then we can run the following commands.

$ pip install Django==4.0.0 # uninstalls 3.2.10 and installs 4.0.0 version of django

$ pip install -U Django # uninstalls 3.2.10 and installs the latest version of it.

Uninstalling packages

To uninstall python packages, we can use pip uninstall [package_name] command. For example, if we want to uninstall django package, we can run the following command:

$ pip uninstall django

since only one version of the package gets installed, we do not need to specify the version of the package to be uninstalled.