Setting up the Python environment

• To setup the Python programming environment, you need to do following steps:
  1. Install pyenv
  2. Install Python
• Windows and Mac users go different route for step1, while step 2 is common.

Install

Installing pyenv

Windows

1. Install WSL2 (Windows service for linux ver.2); following is an example in Windows 10

   1. Open "Windows Power Shell" or "Terminal" as Administrator.
   2. Type wsl --set-default-version 2 (for safe)
   3. Type wsl --install -d Ubuntu.
   4. After installation is done, open Ubuntu in Application.

2. When above doesn't work, check "Windows の機能の有効化、または無効化", then "Linux 用 Windows サブシステム", "仮想マシンプラットフォーム" is ON.

3. Note that WSL makes home directory (/home/your_name) which is different from the Windows user directory (C:\Users\your_name).
4. You can access Windows system from Ubuntu like: cd to Desktop by cd /mnt/c/Users/your_name/Desktop/.

5. It is useful to make symbolic link between Ubuntu and Windows. So, in Ubuntu terminal (not PowerShell), do

   cd
   ln -s /mnt/c/Users/your_user_name/Desktop/ desktop
   

6. If some commands are unavailable (e.g. vi), install them by sudo apt install vim.

7. Install dependencies

   sudo apt update
   sudo apt -y upgrade
   

   then

   sudo apt -y install build-essential libssl-dev zlib1g-dev \
   libbz2-dev libreadline-dev libsqlite3-dev curl \
   libncursesw5-dev xz-utils tk-dev libxml2-dev libxmlsec1-dev libffi-dev liblzma-dev
   

8. Install pyenv

   curl https://pyenv.run | bash
   

Mac

1. Install Homebrew (if not installed)
   • copy command in https://brew.sh/ja/ in the terminal.
2. Install pyenv via Homebrew

   brew install pyenv
   

pyenv configuration

1. Update Bash Configuration. Execute following three lines.

   echo 'export PYENV_ROOT="HOME/.pyenv"′>> /.bashrcecho′exportPATH="HOME/.pyenv"' >> ~/.bashrc
     echo 'export PATH="HOME/.pyenv"′>> /.bashrcecho′exportPATH="PYENV_ROOT/bin:PATH"′>> /.bashrcecho′eval"PATH"' >> ~/.bashrc
     echo 'eval "PATH"′>> /.bashrcecho′eval"(pyenv init -)"' >> ~/.bashrc
   

2. if you are using zsh, replace ~/.bashrc with ~/.zshrc.

3. Reload Bash Configuration

   source ~/.bashrc
   

4. If you are using zsh, replace ~/.bashrc with ~/.zshrc.

Install Python using pyenv

1. List available Python versions

   pyenv install --list
   

2. Choose a version and install it (e.g., Python 3.9.5)

   pyenv install 3.9.5
   

3. It will take some time ...

4. Set Global Python Version

   pyenv global 3.9.5
   

5. Verify Installation

   python --version
   

Installing pip

• pip is the Python package manager.
• If pyenv is installed, pip is automatically installed.
• To not installed, do the following commands to install (both Windows WSL2 and MacOS).
  1. curl https://bootstrap.pypa.io/get-pip.py -o get-pip.py
  2. python get-pip.py
• After installing pip, you can download the library like: pip install numpy.

Python install from source

• When you don't have permission or OS is old, installing Python via pyenv does'nt work.
• In that case, you need to insall Python from source code.
• Make some directory and go there: mkdir python, cd python.
• Get the tar.xz file from web, using wget.
• tar jxvf Python.x.x.x.tar.xz
• ./configure --prefix=/your_home/python.
• make then make install.
• pip is also install. Do not forget to set PATH, and alias to map python -> python3 and pip -> pip3.

Troubleshooting

• 'ImportError: No module named '_tkinter', please install the python3-tk package' (Windows)
  • Do sudo apt install python3-tk.

VScode

• Visual Studio code (VS code) is a free code editor made by Microsoft.
• Works both on Windows and Mac.

  Setup

• Download the installer from https://code.visualstudio.com/
• Install extensions(拡張機能)
  • "Japanese Language Pack" (if you want).
  • "Python"

Wrirting Python script

1. Open a folder where Python script exists
2. After writing the code, save file

3. The "run" command (">" button) to run the script

4. You can change the Python interpreter (like pyenv) by clicking the "Python ..." in the bottom bar.

Google Colaboratory

• Google Colab is a free, cloud-based platform where you can write and run Python code using Jupyter notebooks
• You can use expensive GPUs (graphical proceccing unit) with Google Cloab for free (with some limitations)

Setup

1. Sign in with your Google Account (if exists).
2. Go to Google Colaboratory page in your web browser.
   • https://colab.research.google.com/notebooks/intro.ipynb
3. Create a New Notebook
   • "File(ファイル)" --> "New Notebook(ノートブックを新規作成)" to start a new Python notebook.
4. Copy your notebook to Google Drive.
   • Keep your notebook to Google Drive by clicking "Copy to Drive(ドライブにコピー)".
5. Use the Notebook
   • "+Code(コード)" will insert the code cell in your notebook.
   • In a code cell, you can input Python code.
   • With ">" button, the code will be execured.
6. Saving and Sharing
   • "File" --> "Save" will save your notebook to Google Drive.
   • Click the folder button in left panel then folders are open.
   • You file is save to "drive" --> "Mydrive" (by default).

Notebook-specific grammar

• Putting ! indicates the shell command.
• Putting % indicates the magic command.
  • e.g. To change the directory, specify %cd (not !cd because it generates new shell).
• You can directly edit the Python script (.py) file in Google Colab; click the .py file from the directory tree.

Using GPU

1. "Runtime" tab.
2. "Change the type of Runtime".
3. Choose GPU you want.