Python 3.x: alternative pprint implementation

Question

Standard pprint module is nice when deals with lists, dicts and so on. But sometimes completely unusable with custom classes:

• The only way to make it print usable information about an object of some class is to override __repr__, but what if my class already have nice, eval()'able __repr__ which is not showing the information I want to see in pprint ouput?

• Ok, I will write print-oriented __repr__, but in this case it is impossible to pretty-print something inside my class:

.

class Data:
    def __init__(self):
        self.d = {...}

I can't pretty-print self.d contents, I can return one-line representation only(at least without playing with stacktraces, etc). - Overriding PrettyPrinter is not an option, I dont want to do it every time I want to pretty-print the same class.

So... Is there any alternatives to pprint which allows to make a custom class pretty-printable?

Answer 1

There is an improved and maintained Python 2.x/3.x port of "pretty" library in IPython: https://ipython.readthedocs.io/en/stable/api/generated/IPython.lib.pretty.html

Answer 2

If the pretty module satisfies your needs, you can make it work with Python 3.

1. Download and unpack the pretty.py file.

2. Run 2to3 on it:

   python -m lib2to3 -w pretty.py
   

3. Comment out the following lines:

   569: types.DictProxyType:        _dict_pprinter_factory('<dictproxy {', '}>'),
   580: xrange:                     _repr_pprint,
   

4. Put the file near your script.

5. Import it as usual:

   import pretty
   

Answer 3

for pretty printing you may be looking for __str__ instead of (or as well as) __repr__

e.g.

>>> import datetime
>>> now = datetime.datetime.now()
>>> print now
2013-05-19 13:00:34.085383
>>> print repr(now)
datetime.datetime(2013, 5, 19, 13, 0, 34, 85383)

Answer 4

You can create a generic solution that prints the contents of object fields by subclassing PrettyPrinter. obj.__dict__ will give you a dictionary of all fields of obj.

Or you can just use obj.__class__.__name__ + pformat(obj.__dict__).