python-env-setup

name	python-env-setup
description	Python environment setup — conda/miniconda installation, environment creation, mirror configuration, and activation patterns.
tags	["setup","python","conda","miniconda","environment","mirrors"]

Python Environment Setup

Conda-based Python environment provisioning: install Miniconda, create environments, configure mirrors, and handle activation in scripted contexts.

When to Use

• User asks to create a Python/conda environment
• conda or python commands fail with "command not found"
• Need to configure domestic mirrors for faster package installs
• Setting up a fresh development environment on WSL/Linux

Miniconda Installation

# Download installer
cd /tmp && curl -fsSL -o miniconda.sh https://repo.anaconda.com/miniconda/Miniconda3-latest-Linux-x86_64.sh

# Silent install to ~/miniconda3
bash /tmp/miniconda.sh -b -p $HOME/miniconda3

# Initialize for bash
~/miniconda3/bin/conda init bash

# Accept Terms of Service (conda 26.x+) — REQUIRED before creating environments
conda tos accept --override-channels --channel https://repo.anaconda.com/pkgs/main
conda tos accept --override-channels --channel https://repo.anaconda.com/pkgs/r

Environment Creation

# Activate conda in the current shell (non-login / scripted context)
eval "$($HOME/miniconda3/bin/conda shell.bash hook)"

# Create environment
conda create -y -n <env_name> python=<version>

# Verify
conda activate <env_name> && python --version && which python

Non-Interactive Activation

conda activate does NOT work in non-login shells even after conda init bash. Always use:

eval "$($HOME/miniconda3/bin/conda shell.bash hook)" && conda activate <env_name>

This is the pattern for all scripted terminal commands — source ~/.bashrc is unreliable in non-interactive contexts.

Chinese Mirror Configuration

Conda channels (Tsinghua)

conda config --set show_channel_urls yes
conda config --add channels https://mirrors.tuna.tsinghua.edu.cn/anaconda/pkgs/main/
conda config --add channels https://mirrors.tuna.tsinghua.edu.cn/anaconda/pkgs/free/
conda config --add channels https://mirrors.tuna.tsinghua.edu.cn/anaconda/cloud/conda-forge/

Pip (Tsinghua)

mkdir -p ~/.config/pip
cat > ~/.config/pip/pip.conf << 'EOF'
[global]
index-url = https://pypi.tuna.tsinghua.edu.cn/simple
trusted-host = pypi.tuna.tsinghua.edu.cn
EOF

Pitfalls

Conda 26.x TOS Requirement

Conda 26+ requires explicit Terms of Service acceptance before conda create works. Without it, the command prints a TOS message and exits — the environment is NOT created, but the exit code may still be 0. Always run conda tos accept for both pkgs/main and pkgs/r channels first.

Conda Activate in Scripted Contexts

conda init bash modifies ~/.bashrc, but that file is only sourced in interactive login shells. In non-interactive contexts (background processes, subshells, CI), use the eval "$(conda shell.bash hook)" pattern. source ~/.bashrc in a script is unreliable because many .bashrc files have early return/exit guards for non-interactive shells.

Mirror Channel Order

Conda uses channels in reverse order of addition (last added = highest priority). Add conda-forge last if you want it to take priority over pkgs/main. For most users, the default priority order (main → free → conda-forge) is fine.