Custom Ipython Prompt
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I've grown tired of the standard ipython prompt as it doesn't do much to give me any useful information. The default one gives out a line number that only...

Date: December 20, 2020

I’ve grown tired of the standard ipython prompt as it doesn’t do much to give me any useful information. The default one gives out a line number that only seems to add anxiety as I am working on a simple problem and see that number grow to several hundred. I start to question my ability 🤦‍♂️.

Configuration
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If you already have an ipython config you can move on otherwise check out this post on creating an ipython config.

Ipython-Config </ipython-config/>

The Dream Prompt
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I want something similar to the starship prompt I am using in the shell. I want to be able to quickly see my python version, environment name, and git </glossary/git/> branch.

- python version
- active environment
- git branch

Image: my zsh prompt <https://images.waylonwalker.com/my-zsh-prompt.png>

│ This is my zsh prompt I am using for inspiration

Basic Prompt
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This is mostly boilerplate that I found from various google searches, but this gets me a basic green chevron as my prompt.

[code]
  from IPython.terminal.prompts import Prompts, Token

  class MyPrompt(Prompts):
      def in_prompt_tokens(self, cli=None):
          return [ ( Token.Prompt, "❯ ",), ]

      def out_prompt_tokens(self, cli=None):
          return []

  ip = get_ipython()
  ip.prompts = MyPrompt(ip)

│ The rest of this post will build off of this boilerplate and add to the in_prompt_tokens method of MyPrompt

Colors
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I mostly set the colors of my prompt throughout this post by guessing and trying different attributes under the Token.

Red If Error
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I found that the Prompts subclass has many of the same methods as the ipython object, so I would often use that for inspection. Looking through the ipython class I found a boolean under shell.last_execution_succeeded that would give me if the last execution was successful or not. I did an inline if statemetn to set the color to a Token.Generic.Error if this was false.

[code]
  def in_prompt_tokens(self, cli=None):
      return [
          (
              Token.Prompt
              if self.shell.last_execution_succeeded
              else Token.Generic.Error,
              "❯ ",
          ),
      ]

Python Version
──────────────

Next up to list out the python version that is running. I grabbed the version from platform.python_version, this seemed to get me the most concise version that I was looking for to match the starship prompt.

update imports

[code]
  from platform import python_version

update prompt

[code]
  def in_prompt_tokens(self, cli=None):
      return [
          (
              (Token.Name.Class, "v" + python_version()),
              (Token, " "),
              Token.Prompt
              if self.shell.last_execution_succeeded
              else Token.Generic.Error,
              "❯ ",
          ),
      ]

Python environment
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Since I use conda for my environments I chose to pull the name of the environment from the CONDA_DEFAULT_ENV environment variable that is set by conda when you change your environment.

update imports

[code]
  from platform import python_version
  import os

update prompt

[code]
  def in_prompt_tokens(self, cli=None):
      return [
          (
              (Token.Prompt, "©"),
              (Token.Prompt, os.environ["CONDA_DEFAULT_ENV"]),
              (Token, " "),
              (Token.Name.Class, "v" + python_version()),
              (Token, " "),
              Token.Prompt
              if self.shell.last_execution_succeeded
              else Token.Generic.Error,
              "❯ ",
          ),
      ]

Git Branch
──────────

Git branch was a bit tricky. There might be a better way to get it, but I was sticking with things I knew, the git cli and python. I did need to do a bit of googling to figure out that git has a --show-current option.

getting the current git branch

[code]
  def get_branch():
      try:
          return (
              subprocess.check_output(
                  "git branch --show-current", shell=True, stderr=subprocess.DEVNULL
              )
              .decode("utf-8")
              .replace("\n", "")
          )
      except BaseException:
          return ""

NOTE If this is run form a non-git directory you will quickly find git errors after every command as this function tries to ask for the git branch. Sending stderr to devnull will avoid this inconvenience.

add git branch to prompt

[code]
  def in_prompt_tokens(self, cli=None):
      return [
          (
              (Token.Generic.Subheading, "↪"),
              (Token.Generic.Subheading, get_branch()),
              (Token, " "),
              (Token.Prompt, "©"),
              (Token.Prompt, os.environ["CONDA_DEFAULT_ENV"]),
              (Token, " "),
              (Token.Name.Class, "v" + python_version()),
              (Token, " "),
              Token.Prompt
              if self.shell.last_execution_succeeded
              else Token.Generic.Error,
              "❯ ",
          ),
      ]

Add current directory name
──────────────────────────

I am a big fan of pathlib so that is what I will use to get the path. If I planned on using python <3.6 I would probably use something else, but this is what I know and I can’t think of the last time I used <3.6> for anything.

update imports

[code]
  from pathlib import Path

add git branch to prompt

[code]
  def in_prompt_tokens(self, cli=None):
      return [
          (
              (Token, ""),
              (Token.OutPrompt, Path().absolute().stem),
              (Token, ""),
              (Token.Generic.Subheading, "↪"),
              (Token.Generic.Subheading, get_branch()),
              (Token, " "),
              (Token.Prompt, "©"),
              (Token.Prompt, os.environ["CONDA_DEFAULT_ENV"]),
              (Token, " "),
              (Token.Name.Class, "v" + python_version()),
              (Token, " "),
              Token.Prompt
              if self.shell.last_execution_succeeded
              else Token.Generic.Error,
              "❯ ",
          ),
      ]

Final Script
────────────

That’s it for my prompt at the moment. I have been using it for about a week. It seems to have everything I need so far, and skips on things I don’t need.

Enjoy the full script.

my final prompt

[code]
  from IPython.terminal.prompts import Prompts, Token
  from pathlib import Path
  import os
  from platform import python_version
  import subprocess

  def get_branch():
      try:
          return (
              subprocess.check_output(
                  "git branch --show-current", shell=True, stderr=subprocess.DEVNULL
              )
              .decode("utf-8")
              .replace("\n", "")
          )
      except BaseException:
          return ""


  class MyPrompt(Prompts):
      def in_prompt_tokens(self, cli=None):
          return [
              (Token, ""),
              (Token.OutPrompt, Path().absolute().stem),
              (Token, " "),
              (Token.Generic.Subheading, "↪"),
              (Token.Generic.Subheading, get_branch()),
              (Token, " "),
              (Token.Prompt, "©"),
              (Token.Prompt, os.environ["CONDA_DEFAULT_ENV"]),
              (Token, " "),
              (Token.Name.Class, "v" + python_version()),
              (Token, " "),
              (Token.Name.Entity, "ipython"),
              (Token, "\n"),
              (
                  Token.Prompt
                  if self.shell.last_execution_succeeded
                  else Token.Generic.Error,
                  "❯ ",
              ),
          ]

      def out_prompt_tokens(self, cli=None):
          return []


  ip = get_ipython()
  ip.prompts = MyPrompt(ip)

Want automatic imports??
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Smoother Python with automatic imports | pyflyby </pyflyby/>

│ This article covers how I setup automatic imports in ipython