__dict__ in math library

[akbarza]

hi
i saw that there is no "__dict__" in math library. namely:

import math
"__dict__ " in dir(math)

the result will be False. but when i write

math.__dict__.items() 

, a large dict_items object will be shown in idle.
how is it possible when there is not __dict__ in math lib,then there is math.__dict__.items() ?
thanks

[buran]

https://docs.python.org/3/library/stdtyp...attributes

Special Attributes

The implementation adds a few special read-only attributes to several object types, where they are relevant. Some of these are not reported by the dir() built-in function.

object.__dict__

A dictionary or other mapping object used to store an object’s (writable) attributes.

[akbarza]

hi
as i said before, the

math.__dict__.items()

gives a dict_items object with first element( as i run) :
('__names__','math') .
how can I get this element? how can I get '__names__' ? and how for 'math'?
thanks

[deanhystad]

Get attribute values the same way as any other object.

import math

print(math.__name__)
print(getattr(math, "__name__"))

You should not be using __dict__ directly. Not all objects have __dict__. Some have __slots__, but dir() works for both.

class Base:
    __slots__ = "foo", "bar"


class Right(Base):
    __slots__ = ("baz",)


r = Right()
print(dir(r))
print(r.__dict__)

Error:
Traceback (most recent call last):
  File "...", line 11, in <module>
    print(r.__dict__)
AttributeError: 'Right' object has no attribute '__dict__'. Did you mean: '__dir__'?

[akbarza]

hi deanhystad
is there a way to print all elements in math.__dict__.names()? namely as:
('__names__','math')
( .......)
(...)
.
.
.

how?

[akbarza]

hi
excuse me for more questions
math.__dict__.names() is of type dict_items type. what is the difference between 'dict_items' type and the 'dict' type?
in page https://realpython.com/python-eval-funct...with-input there is a code( large code, so i not import here) that contains the below line:

ALLOWED_NAMES = {
    k: v for k, v in math.__dict__.items() if not k.startswith("__")
}

so if I write:

for k, v in math.__dict__.items():
      print(k,v)

it prints something.
but for a dictionary as :

dic={'x': 1, 'y': 2, 'z': 3, 'w': 4}

then :

for a,b in dic:
    print(a,b)

then idle creates an error:

Error:
Traceback (most recent call last):
  File "<pyshell#39>", line 1, in <module>
    for a,b in dic:
ValueError: not enough values to unpack (expected 2, got 1)

what is the difference between them? thanks for more explain.

[buran]

when you iterate over dict, you iterate over keys only, i.e. for key in some_dict: is equivalent to for key in some_dict.keys():. You need to iterate over some_dict.items() if you want to get both key and value, i.e. you get (key, value) tuple which you unpack, in your case into a and b respectively