pprinting a Dataclass with a numpy array field and None as default fails

[aseltmann]

• PrettyPrinter version: 0.18.0
• Python version: 3.9.16 (main, Dec 7 2022, 01:11:51) [GCC 9.4.0]
• Operating System: uname_result(system='Linux', node='73b98b6d221c', release='5.10.147+', version='# 1 SMP Sat Dec 10 16:00:40 UTC 2022', machine='x86_64')

Description

I use dataclasses with numpy array fields and noticed that prettyprinting fails when the typing for init values is e.g. Optional[np.ndarray] or Union[np.ndarray, None] and additionally None is specified as default.

• The same did not happen e.g. for Optional[List] = None.
• This did not happen for Union[np.ndarray, str] = 'test'
• The system I use this on is a Google Colab (see info above), which currently still runs Python 3.9 and might have additional specifics I don't know about.

What I Did

Input:

import numpy as np

from dataclasses import dataclass
from typing import Optional
from prettyprinter import pprint, install_extras
install_extras()

@dataclass
class Test1:
    another_array: np.ndarray
    maybe_array: Optional[np.ndarray]

@dataclass
class Test2:
    another_array: np.ndarray
    maybe_array: Optional[np.ndarray] = None

array = np.array([1, 2, 3, 4])

pprint(Test1(maybe_array=array, another_array=array))
print('---')
pprint(Test2(maybe_array=array, another_array=array))

Output:

Test1(
    another_array=numpy.ndarray([1, 2, 3, 4]),
    maybe_array=numpy.ndarray([1, 2, 3, 4])
)
---
Test2(another_array=array([1, 2, 3, 4]), maybe_array=array([1, 2, 3, 4]))
/usr/local/lib/python3.9/dist-packages/prettyprinter/prettyprinter.py:340: UserWarning: The pretty printer for Test2, prettyprinter.prettyprinter._repr_pretty, raised an exception. Falling back to default repr.

Traceback (most recent call last):
  File "/usr/local/lib/python3.9/dist-packages/prettyprinter/prettyprinter.py", line 387, in _run_pretty
    doc = pretty_fn(value, ctx)
  File "/usr/local/lib/python3.9/dist-packages/prettyprinter/prettyprinter.py", line 424, in _repr_pretty
    return fn(value, ctx)
  File "/usr/local/lib/python3.9/dist-packages/prettyprinter/extras/dataclasses.py", line 40, in pretty_dataclass_instance
    if field_def.default != getattr(value, field_def.name):
ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()

  warnings.warn(