Type the name of an object in python interpreter - what method is it called?

Question

What method is it called when I type the name of the object? I always thought that it was calling either repr or str but that doesn't hold in case of the PageObject of PyPDF2. As you can see, the output of __repr__ or __str__ is different to the one we get when we type the name of the variable in the interactive console.

>>> reader = PdfFileReader(f)
>>> page = reader.pages[0]
>>> page

'/Encoding': {'/Differences': [32,
      '/space',
      40,
      '/parenleft',
      '/parenright',
      46,
      '/period',
      '/slash',
      '/zero',
      '/one',
      '/two',
      '/three',
      '/four',
      '/five',
      '/six',
      56,
      '/eight',
      '/nine',
      69,
      ...

>>> page.__str__()

"{'/Annots': [], '/Contents': IndirectObject(12, 0), '/Group': {'/CS': '/DeviceRGB', '/S': '/Transparency', '/Type': '/Group'}, '/MediaBox': RectangleObject([0, 0, 460.8, 345.6]), '/Parent': IndirectObject(2, 0), '/Resources': IndirectObject(8, 0), '/Type': '/Page', '/ArtBox': RectangleObject([0, 0, 460.8, 345.6]), '/BleedBox': RectangleObject([0, 0, 460.8, 345.6]), '/CropBox': RectangleObject([0, 0, 460.8, 345.6]), '/TrimBox': RectangleObject([0, 0, 460.8, 345.6])}"
```

>>> page.__repr__()

<same-as-above>

P.S. Probably there's an answer out there for this question and it's just that I haven't typed my query correctly.

UPDATE I observe this behavior in IPython (version 5.5.0). Running with the builtin REPL the output I get when typing the variable name matches the repr output.

Possible duplicate of [Difference between \_\_str\_\_ and \_\_repr\_\_?](https://stackoverflow.com/questions/1436703/difference-between-str-and-repr) — Olvin Roght, Sep 30 '19 at 15:06
@OlvinRoght I don't think it is a duplicate. output of typing the object name is different than either `repr` or `str`. — bergercookie, Sep 30 '19 at 15:10

score 2 · Accepted Answer · answered Oct 01 '19 at 12:07

Using a variable name (like x) in the standard Python REPL is equivalent to print(repr(x)). You can convince yourself of that (and that it is not simply print(x)) by implementing __repr__ and __str__ yourself:

>>> class Test:
...   def __repr__(self):
...     return 'using repr\nmagic, isn\'t it?'
...   def __str__(self):
...     return 'using str'
... 
>>> Test()
using repr
magic, isn't it?
>>> repr(Test())
"using repr\nmagic, isn't it?"
>>> print(Test())
using str
>>> print(repr(Test()))
using repr
magic, isn't it?

But you are using IPython, which features rich outputs; which means that some objects get special treatment when being displayed. Dicts are such objects; and since your page is a special kind of dict:

Help on PageObject in module PyPDF2.pdf object:

class PageObject(PyPDF2.generic.DictionaryObject)
 |  PageObject(pdf=None, indirectRef=None)
 |  
 |  This class represents a single page within a PDF file.  Typically this
 |  object will be created by accessing the
 |  :meth:`getPage()<PyPDF2.PdfFileReader.getPage>` method of the
 |  :class:`PdfFileReader<PyPDF2.PdfFileReader>` class, but it is
 |  also possible to create an empty page with the
 |  :meth:`createBlankPage()<PageObject.createBlankPage>` static method.
 |  
 |  :param pdf: PDF file the page belongs to.
 |  :param indirectRef: Stores the original indirect reference to
 |      this object in its source PDF
 |  
 |  Method resolution order:
 |      PageObject
 |      PyPDF2.generic.DictionaryObject
 |      builtins.dict
 |      PyPDF2.generic.PdfObject
 |      builtins.object
[…snip…]

Then you get the special dict display; which is akin to using pprint.pprint:

>>> import pprint
>>> from PyPDF2 import PdfFileReader
>>> PDF = PdfFileReader('…')
>>> page = PDF.pages[0]
>>> pprint.pprint(page)
{'/Contents': IndirectObject(2, 0),
 '/Group': {'/CS': '/DeviceRGB',
            '/I': <PyPDF2.generic.BooleanObject object at 0x7faa67639310>,
            '/S': '/Transparency'},
 '/MediaBox': [0, 0, 842, 595],
 '/Parent': IndirectObject(6, 0),
 '/Resources': IndirectObject(23, 0),
 '/Rotate': 0,
 '/Type': '/Page'}

Type the name of an object in python interpreter - what method is it called?

1 Answers1