# Concrete Objects Layer

The functions in this chapter are specific to certain Python object types. Passing them an object of the wrong type is not a good idea; if you receive an object from a Python program and you are not sure that it has the right type, you must perform a type check first; for example, to check that an object is a dictionary, use `PyDict_Check()`. The chapter is structured like the “family tree” of Python object types.

Warning

While the functions described in this chapter carefully check the type of the objects which are passed in, many of them do not check for `NULL` being passed instead of a valid object. Allowing `NULL` to be passed in can cause memory access violations and immediate termination of the interpreter.

## Fundamental Objects

This section describes Python type objects and the singleton object `None`.

- Type Objects
  - Creating Heap-Allocated Types
    - Type slot IDs
  - Soft-deprecated API
- The `None` Object

## Numeric Objects

- Integer Objects
  - Export API
  - PyLongWriter API
  - Deprecated API
- Boolean Objects
- Floating-Point Objects
  - Pack and Unpack functions
    - Pack functions
    - Unpack functions
- Complex Number Objects
  - Complex Numbers as C Structures

## Sequence Objects

Generic operations on sequence objects were discussed in the previous chapter; this section deals with the specific kinds of sequence objects that are intrinsic to the Python language.

- Bytes Objects
- PyBytesWriter
  - Create, Finish, Discard
  - High-level API
  - Getters
  - Low-level API
- Byte Array Objects
  - Type check macros
  - Direct API functions
  - Macros
- Unicode Objects and Codecs
  - Unicode Objects
    - Unicode Type
    - Unicode Character Properties
    - Creating and accessing Unicode strings
    - Locale Encoding
    - File System Encoding
    - wchar_t Support
  - Built-in Codecs
    - Generic Codecs
    - UTF-8 Codecs
    - UTF-32 Codecs
    - UTF-16 Codecs
    - UTF-7 Codecs
    - Unicode-Escape Codecs
    - Raw-Unicode-Escape Codecs
    - Latin-1 Codecs
    - ASCII Codecs
    - Character Map Codecs
    - MBCS codecs for Windows
  - Methods and Slot Functions
  - PyUnicodeWriter
  - Deprecated API
- Tuple Objects
- Struct Sequence Objects
- List Objects

## Container Objects

- Dictionary objects
  - Dictionary view objects
  - Frozen dictionary objects
  - Ordered dictionaries
- Set Objects
  - Deprecated API

## Function Objects

- Function Objects
- Instance Method Objects
- Method Objects
- Cell Objects
- Code Objects
- Code Object Flags
- Extra information

## Other Objects

- File objects
  - Soft-deprecated API
- Module Objects
  - Module definition
    - Metadata slots
    - Feature slots
    - Creation and initialization slots
  - Module state
    - Slots for defining module state
    - Module token
  - Creating extension modules dynamically
  - Module definition struct
  - Support functions
    - Module lookup (single-phase initialization)
- Iterator Objects
  - Range Objects
  - Builtin Iterator Types
  - Other Iterator Objects
- Descriptor Objects
  - Built-in descriptors
- Slice Objects
  - Ellipsis Object
- MemoryView objects
- Pickle buffer objects
- Weak Reference Objects
- Capsules
- Sentinel objects
- Frame objects
  - Frame locals proxies
  - Legacy local variable APIs
  - Internal frames
- Generator Objects
  - Asynchronous Generator Objects
  - Deprecated API
- Coroutine Objects
- Context Variables Objects
- Objects for Type Hinting

## C API for extension modules

- Curses C API
- Internal data
- DateTime Objects
- Internal data