> For the complete documentation index, see [llms.txt](https://www.techwithtyler.dev/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://www.techwithtyler.dev/coding-and-cli-tooling/coding-and-scripting/python.md).

# Python

{% hint style="warning" %}
While `pyenv` and `pipx` can still be used, `uv` is quickly becoming the standard/favorite for many.

I've kept the guides for these tools below, but strongly suggest checking out `uv` instead!
{% endhint %}

## Overview

* As Python gets updated, older code will cease to run due to changes in Python syntax and functionality
* To resolve this, we can run code in containers, but that adds a level of complexity 
* Another solution is to use `uv` (or [pyenv](#pyenv) and [pipx](#pipx)) and run the code in virtualized environments with the required version of Python

{% hint style="danger" %}
`uv` only supports Python v3+ so use `pyenv` if you need Python v2.x
{% endhint %}

### Installation

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```bash
brew install uv
```

{% endcode %}

### View Available Python Versions

#### **List all available python versions (both installed and not)**

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```bash
uv python list 
```

{% endcode %}

#### **List only installed python versions**

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```bash
uv python list --only-installed
```

{% endcode %}

#### **List only python versions not already installed**

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```bash
uv python list --only-downloads
```

{% endcode %}

### Using Specific Python Versions

#### **Install one or more versions of python**

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```bash
uv python install 3.8.5
uv python install 3.8.5 3.14.0
```

{% endcode %}

#### **Install a tool with a specific python version**

{% code overflow="wrap" %}

```bash
uv tool install principalmapper --python 3.9.21
```

{% endcode %}

### Set up a Virtual Environment

#### **Creates a virtual environment with python v3.14.0**

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```bash
uv venv tmp-py3-14 --python 3.14.0
source tmp-py3-14/bin/activate
```

{% endcode %}

### Installing Required Modules

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```zsh
## script doesn't execute because of missing module
python3 ./my-script.py
# output
ModuleNotFoundError: No module named 'colorama'
```

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{% code overflow="wrap" %}

```zsh
## install the module(s) via a req file or individually
uv pip install -r requirements.txt
uv pip install colorama
```

{% endcode %}

### Managing Tools Installed with `uv`

**List installed tools**

```
uv tool list 
```

**Install tools**

* This works just like `pipx` or `pip`

{% code overflow="wrap" %}

```bash
uv tool install <tool>
```

{% endcode %}

**Uninstall tools**

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```bash
uv tool uninstall <tool>
```

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***

***

## Old — Examples

### Old — Install and Run a Python App with a Specific Python Version

* [PrincipalMapper](https://github.com/nccgroup/PMapper) (pmapper) is a tool that requires Python version 3.9 to run (it errors out otherwise)

{% code overflow="wrap" %}

```bash
# list available versions of python to install
pyenv install --list

# install python 3.9.21
pyenv install 3.9.21

# set version of python that pyenv will use
pyenv global 3.9.21

# validate version is set (should match 3.9.21 for this example)
python --version 

# install the tool, principalmapper (aka pmapper)
pipx install --python $(pyenv which python) principalmapper
```

{% endcode %}

### Old — Set up a Python Virtual Environment&#x20;

* We can set up a virtual environment to run any version of Python we want
* This is useful for isolating your Python code/packages without impacting your system configuration

{% code overflow="wrap" %}

```bash
# install python 2.7.18
pyenv install 2.7.18

# make a directory to work in 
mkdir venv-tyler-python-2-7-18

# create virtualenv for python 2.7.18
pyenv virtualenv 2.7.18 venv-tyler-python-2-7-18

# change into the directory
cd venv-tyler-python-2-7-18

# set directory for virtualenv
pyenv local venv-tyler-python-2-7-18

# validate python version (should match 2.7.18)
python --version
```

{% endcode %}

### Parsing JSON

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```bash
"ffuf -w /opt/useful/SecLists/Discovery/DNS/namelist.txt -u http://<target IP> -H HOST: FUZZ.<target domain> -o possible-subdomains.json"
```

{% endcode %}

{% code overflow="wrap" %}

```python
import json

json_dump = "./possible-subdomains.json"

with open(json_dump) as f:
    data = json.load(f)

for host in data["results"]:
    print(host["host"], host["url"]) # print out the host & URL
```

{% endcode %}

### View installed modules

{% code overflow="wrap" %}

```python
python3 -c 'help("modules")'

[SNIP]
Cryptodome          cairo               ldb                 retrying
Cython              calendar            lib2to3             rfc3986
IPy                 catfish             libfuturize         rfc3987
IPython             catfish_lib         libpasteurize       rich
[SNIP]
```

{% endcode %}

### View pip modules

```python
pip list

Package    Version
---------- -------
pip        20.3.4
setuptools 44.1.1
wheel      0.37.1
xlrd       2.0.1
```

***

## Old — Pyenv

### Installation

* [pyenv](https://github.com/pyenv/pyenv?ref=playfulpython.com) is a useful tool for letting us quickly download and switch between multiple versions of Python
* Full installation instructions can be [found here](https://github.com/pyenv/pyenv?tab=readme-ov-file#installation)

{% code overflow="wrap" %}

```bash
# install on linux
curl https://pyenv.run | bash

# add to ~/.zshrc
echo 'export PYENV_ROOT="$HOME/.pyenv"' >> ~/.zshrc
echo '[[ -d $PYENV_ROOT/bin ]] && export PATH="$PYENV_ROOT/bin:$PATH"' >> ~/.zshrc
echo 'eval "$(pyenv init - zsh)"' >> ~/.zshrc

# restart shell for PATH changes to take effect
exec "$SHELL"

# install python build dependencies (see install instructions as this is specific to your OS)
# this is for Debian-based systems (Ubuntu, Kali, Parrot, etc.)
sudo apt update; sudo apt install build-essential libssl-dev zlib1g-dev \
libbz2-dev libreadline-dev libsqlite3-dev curl git \
libncursesw5-dev xz-utils tk-dev libxml2-dev libxmlsec1-dev libffi-dev liblzma-dev
```

{% endcode %}

### Useful commands

{% code overflow="wrap" %}

```bash
# view all python versions installed with pyenv
pyenv versions

# set global (default) python version for pyenv
pyenv global 3.x.x

# set local (directory) python version for pyenv (trumps global). Adds `.python-version` to directory. All pyenv commands in this directory will use this python version
pyenv local 3.x.x

# view available python versions
pyenv install --list
```

{% endcode %}

***

## Old — Pipx

### Installation

* [pipx](https://github.com/pypa/pipx) is a useful tool for installing and running python code and apps in isolated virtual environments
* Full installation instructions can be [found here](https://github.com/pypa/pipx?tab=readme-ov-file#install-pipx)

{% code overflow="wrap" %}

```bash
# install on linux
sudo apt update
sudo apt install pipx
pipx ensurepath
sudo pipx ensurepath --global # optional to allow pipx actions with --global argument
```

{% endcode %}

### Useful commands

{% code overflow="wrap" %}

```bash
# install package for user (~/.local/bin)
pipx install trufflehog

# install package for all users (/usr/local/bin/)
sudo pipx install trufflehog --global

# view installed packages
pipx list
sudo pipx list  

# uninstall packages
pipx uninstall trufflehog
sudo pipx uninstall trufflehog --global
```

{% endcode %}