Custom Ipython Prompt
=====================

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

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

Ipython-Config [1]

## The Dream Prompt

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 branch.

* python version
* active environment
* git branch

![my zsh prompt](https://images.waylonwalker.com/my-zsh-prompt.png)

> This is my zsh prompt I am using for inspiration

## Basic Prompt

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

``` python
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

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

## Red If Error

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.

``` python
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_

``` python
from platform import python_version
```

_update prompt_

``` python
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

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_

``` python
from platform import python_version
import os
```

_update prompt_

``` python
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_

``` python
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_

``` python
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 `` for anything.

_update imports_

``` python
from pathlib import Path
```

_add git branch to prompt_

``` python
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_

``` python
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??

Smoother Python with automatic imports | pyflyby [2]

> This article covers how I setup automatic imports in ipython

References:
[1]: /ipython-config/
[2]: /pyflyby/