pip

pip is the package installer for Python. It allows you to install and manage additional libraries and dependencies that are not included in the Python standard library.

Installation and Basic Usage

Install a Package:
```
pip install requests
```
Uninstall a Package:
```
pip uninstall requests
```
Check Installed Packages:
```
pip list
```
Check for Package Updates:
```
pip list --outdated
```

Managing Dependencies

Install from requirements.txt: Create a requirements.txt file with a list of packages and versions:
```
requests==2.28.1
numpy==1.24.2
```
Install dependencies:
```
pip install -r requirements.txt
```
Freeze Installed Packages: Generate a requirements.txt file from the current environment:
```
pip freeze > requirements.txt
```
Upgrade a Package:
```
pip install --upgrade requests
```

Environment and Compatibility

Create a Virtual Environment: Although pip itself doesn’t create virtual environments, it works seamlessly with venv or virtualenv.
```
python -m venv myenv
```
Activate the Virtual Environment:
- On Windows:
```
myenv\Scripts\activate
```
- On macOS/Linux:
```
source myenv/bin/activate
```
Check pip Version:
```
pip --version
```
Upgrade pip:
```
pip install --upgrade pip
```

Scripting and Automation

Install Multiple Packages in a Single Command:
```
pip install requests numpy pandas
```
Automate Package Installation: Use shell scripts or batch files to automate installation in multiple environments.

Other

In pip, the concept of "development" dependencies (i.e., packages needed only for development, not for production) is not directly supported in the same way as some other tools like Poetry or Pipenv. However, you can manage development dependencies in a few ways using pip:

Using requirements.txt with Separate Files

You can maintain separate requirements.txt files for different environments, such as one for production and one for development.
Production requirements.txt:
- List only the packages required for your application to run in production
```
requests==2.28.1
numpy==1.24.2
```
Development requirements-dev.txt:
- List the additional packages needed for development, such as testing and linting tools.
```
pytest==7.4.0
flake8==6.0.0
```
To install production dependencies:
```
pip install -r requirements.txt
```
To install development dependencies:
```
pip install -r requirements-dev.txt
```
Alternatively, you can include development dependencies in a single file with markers or comments, and install them conditionally.