simpleformatter

A quick way to add custom versatile formatting to objects

• Free software: MIT license
• Python version 3.7+ (but 3.6 might work, too- haven't tried it yet)
• Documentation: https://simpleformatter.readthedocs.io. (not set up yet)

Introduction

f-strings are taking over the python world. But it requires a lot of effort to take a function like this:

>>> def format_camel_case(string):
...     """camel cases a sentence"""
...     return ''.join(s.capitalize() for s in string.split())
...

...and direct the formatting of a user object to that function by customizing the f-string syntax:

>>> my_phrase = MyString("lime cordial delicious")
>>> f"{my_phrase:camcase}"
'LimeCordialDelicious'

...or, perhaps use f-strings to send measurements to a unit conversion formatting function:

>>> x = Measurement(12, 'inches')
>>> f'{x:.1ft}'
'1.0 ft'
>>> f'{x:.2cm}'
'30.48 cm'
>>> f'{x:.3m}'
'0.305 m'

Implementing these examples requires overriding the __format__ method, and including all the formatting logic tied up as part of the class. What a bummer. simpleformatter provides a better way.

Library API

The primary API consists of 3 decorators:

>>> from simpleformatter import formattable, target, formatmethod

formattable decorator

Use the formattable decorator to associate a specifier key with a previously defined formatting function:

>>> @formattable(camcase=format_camel_case)
... class MyStr(str): ...
...
>>> f'{MyStr("lime cordial delicious"):camcase}'
'LimeCordialDelicious'

target decorator

Use the target decorator to mark a formatting function as a formatting specifier(s) target:

>>> length_dict = {'in': 1, 'ft': 1/12, 'cm': 2.54, 'mm': 25.4, 'm': 0.0254}
>>> def convert(value, unit):
...     return length_dict[unit] * value
...
>>> import itertools as it
>>> @target(*length_dict)  # specifiers are: in, ft, cm, mm, m
... def format_convert(value, unit_spec):
...     unit = ''.join(reversed(list(it.takewhile(lambda x: x.isalpha(), reversed(unit_spec)))))
...     return f'{convert(value, unit):{unit_spec[:-len(unit)]}} {unit}'
...

Now the decorated formatting function will act as a target for any decorated user class:

>>> @formattable
... class Diameter(float): ...
...
>>> @formattable
... class Depth(float): ...
...
>>> f"{Diameter(8.45):.3ft}")
'0.704 ft'
>>> f"{Depth(3.77):.4mm}")
'95.76 mm'

formatmethod decorator

The formatmethod decorator makes the method a target of the formatting specifier(s) for that class only:

>>> @formattable
... class Data(float):
...     @formatmethod('Bytes', 'B')
...     def _repr_b_(self):
...         return f'{self} Bytes'
...     @formatmethod('KB')
...     def _repr_kb_(self):
...         return f'{self/1024} KB'
...     @formatmethod('MB')
...     def _repr_mb_(self):
...         return f'{self/1024**2} MB'
...     @formatmethod('GB')
...     def _repr_gb_(self):
...         return f'{self/1024**3} GB'
...
>>> f'{Data(112_113_254):B}'
'112113254.0 Bytes'
>>> f'{Data(112_113_254):MB}'
'106.91953086853027 MB'
>>> f'{Data(112_113_254):GB}'
'0.1044136043637991 GB'

ToDo

• Tox and docs are not set up yet
• Some docstring tests are still broken (bad references in them)
• Need to decide if supporting 3.6, or just 3.7+

Credits

This package was created with Cookiecutter and the audreyr/cookiecutter-pypackage project template.