# 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
- The `None` Object

## Numeric Objects

- Integer Objects
- Boolean Objects
- Floating-Point Objects
  - Pack and Unpack functions
    - Pack functions
    - Unpack functions
- Complex Number Objects
  - Complex Numbers as C Structures
  - Complex Numbers as Python Objects

## 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
- 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
- Tuple Objects
- Struct Sequence Objects
- List Objects

## Container Objects

- Dictionary Objects
  - Dictionary View Objects
  - Ordered Dictionaries
- Set Objects

## Function Objects

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

## Other Objects

- File Objects
- Module Objects
  - Initializing C modules
    - Single-phase initialization
    - Multi-phase initialization
    - Low-level module creation functions
    - Support functions
  - Module lookup
- 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
- Frame Objects
  - Frame Locals Proxies
  - Legacy Local Variable APIs
  - Internal Frames
- Generator Objects
  - Asynchronous Generator Objects
- Coroutine Objects
- Context Variables Objects
- Objects for Type Hinting

## C API for extension modules

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