displayhooks

displayhooks

It's a micro library for manipulating sys.displayhook.

When you need to change the standard behavior of displayhook, with this library you will do it:

• declaratively
• compactly
• beautifully

Table of contents

• Quick start
• Change the displayed value
• Prohibiting the display of certain types of values
• Automatic recovery of the default hook

Quick start

Install it:

pip install displayhooks

And use:

import sys
from displayhooks import not_display

not_display(int)

sys.displayhook('Most of the adventures recorded in this book really occurred; one or two were experiences of my own, the rest those of boys who were schoolmates of mine.')
#> 'Most of the adventures recorded in this book really occurred; one or two were experiences of my own, the rest those of boys who were schoolmates of mine.'
sys.displayhook(666)
# [nothing!]

Change the displayed value

You can declaratively declare a converter function for the printed values. What it returns will be used to call the original displayhook function.

import sys
from displayhooks import converted_displayhook

@converted_displayhook
def new_displayhook(value):
    return value.lower()

sys.displayhook("What’s gone with that boy, I wonder? You TOM!")
#> 'what’s gone with that boy, i wonder? you tom!'

If your function returns None, nothing will be printed.

Prohibiting the display of certain types of values

You can disable the display of certain data types, similar to how NoneType values are ignored by default.

You could already see a similar example above, let's look at it again:

import sys
from types import FunctionType
from displayhooks import not_display

not_display(FunctionType)

sys.displayhook('Nothing! Look at your hands. And look at your mouth. What is that truck?')
#> 'Nothing! Look at your hands. And look at your mouth. What is that truck?'
sys.displayhook(lambda x: x)
# [nothing!]

In this example, you can see that we have disabled the display for functions, but all other data types are displayed unchanged.

Automatic recovery of the default hook

You can limit the impact on sys.displayhook only to the code inside a function. If you hang the autorestore_displayhook decorator on it, after exiting the function, the displayhook that was installed before it was called will be automatically restored:

import sys
from types import FunctionType
from displayhooks import not_display, autorestore_displayhook

@autorestore_displayhook
def do_something_dangerous():
    not_display(FunctionType)
    sys.displayhook(do_something_dangerous)
    # [nothing!]

do_something_dangerous()

sys.displayhook(do_something_dangerous)
#> <function do_something_dangerous at 0x104c980e0>