Python Idiom (raw has better view)

python_idiom.mdown

Python Idioms

#

• *args : tuple
• **kwargs : dict
• [[]]*10 创建对同一个列表5次引用的列表
• __slots__: compile-time restrict attribute
• @/__matmul__ in py3

A

• abc module : virtual (abstact) base class
• • register
• • subclasshook
• • @abstractmethod (compare to @classmethod, @staticmethod, slots)
• async/await
• • async with
• • • __aenter__/__aexit__/__aiter__
• • async def
• analyzer
• • inspect module
• • • signature
• • ast module
• • parser module
• • pdb module
• • dis module (python bytecode)

B

• bound
• • unbound

C

• c3 algorithm
• • 查找: instance.dict -> Parentest.dict -> instance.class.dict (instance.class.__mro__顺序)
• contextlib module
• • enter + exit => try + yield
• collection module
• • namedtuple
• • OrderDict
• • heapq
• coroutine : yield (from)
• callback / delegate
• closure
• • nonlocal
• compare
• • in Python 2, you can < compare anything to anything.
• ctypes
• comprehension
• • list
• • dict
• • • print {i : chr(65+i) for i in range(4)} -> {0 : 'A', 1 : 'B', 2 : 'C', 3 : 'D'}

D

• descriptor
• • get
• • set
• • delete
• decorator (AOP)
• duck typing
• Database ORM
• 单例
• • new
• • 模块常量
• Decimal
• Default parameter
• • 默认列表只在函数被定义的那一刻创建一次 def func(l = [])
• del 循环引用 => gc 不工作

E

• Exception
• • rethrow: raise ... from ...
• • sys.exceptionhook

F

• functools module
• • @lru_cache
• • total_ordering : #include <boost/operator.hpp>
• • partial : bind
• • fp method
• • • reduce/map/filter
• • singleddispatch (overload without type hinting)
• • wrapper
• • • @wraps : save name, doc
• faulthandler in py3
• format
• • ref
• • align/padding/named-variable(Formatted string literals)
• • F-string
• • • name = "Test" f"My app name is {name}."

G

• get : descriptor
• getattr : class/base property
• getattribute : instance property
• get -> getattr -> getattribute
• generator : yield/next
• • GeneratorExit

H

I

• iterator
• • iter : return self
• • next : return data | StopIteration
• itertools modules : just like #include <numeric>
• import hacking
• • module q
• • sys.modules[name] = Class
• • module/package/loader
• • path/file/name
• • all/version
• • PEP 302
• • importlib
• • _temp = import('spam.ham', globals(), locals(), ['eggs', 'sausage'], -1)
• init_subclass
• • ref

J

K

• Keyword only arguments
• • def foo(*, arg1=1, arg2=None) in python3 (force named params)

L

• logging module
• LEGB
• • locals->enclosing->globals->builtins
• • • assignment will make variables local (copy) (use global/nonlocal to prevent)

M

• mro (method resolution order)
• metaclass <-> class <-> instance
• • prepare
• • new/init
• • call
• • ref
• mutable / immutuble
• • reference problem
• magic method
• • xxx => xxx(class)
• Mixin
• method wrapper (slot wrapper)
• • Cython implementation

N

O

• os module

P

• PyObject
• PyType
• @property (public type name {get; set;})
• • .getter
• • .setter
• • __property: private => _classname__property
• • _property: protect => _property

Q

R

• re module: regex (no unicode property \p{CN})
• • lookaround ?= ?! ?<= ?<!
• • capture ?:
• • name ?P ?P=name
• • greedy .*?
• • comment ?#
• • \number group
• • Regular expression -> NFA (POSIX NFA) -> DFA(BNF)
• Resize strategy
• • 8->32->...-> >50000 x2->x2 (set, dict)
• • (size+1 >> 3) + (size+1 < 9 ? 3 : 6) (list, 0, 4, 8, 16, 25, 35, 46, 58, 72, 88, ...) （\approx 1.125)

S

• science modules
• • numpy
• • sympy
• • matplotlib
• sys module
• • sys._getframe()
• • • | f_back # 上一个栈帧对象(谁调用自己)
• • • | f_builtins # 内置名字空间
• • • | f_locals # local名字空间
• • • | f_globals # 全局名字空间
• • • | f_code # 帧指向的 codeObject对象
• • • | f_cellvars # 内部闭包使用的freevar
• • • | f_freevars # 闭包引用的freevar
• • • | f_localsplus # 局部变量 + cell对象 + free对象 + 运行时栈
• • • • closure
• • • • | co_name # code block的名字, 通常是类名或者函数名 /* string (name, for reference) */
• • • • | co_names # code block中所有的名字 /* list of strings (names used) */
• • sys.getrefcount()
• • • ref
• super()
• • new-style class
• • just call the next function in the mro links (generated by C3)
• • will continue call if super() in base classes
• small integer pool : -5~257
• Recursive stack overflow
• • trampoline
• • continuation-pass-style (callback)
• • raise exception and pass value
• str (py3)
• • wchar_t
• • utf-8 bytes (unicodedata_db) : UCS-1/UCS-2/UCS-4
• star expression
• • _1, *_, _5 = [1, 2, 3, 4, 5]
• • _1, _2, * = range(10)

T

• typing module
• • List
• • Callable[..., ReturnType]
• • Generics
• • • Mapping
• • • Sequence
• • • TypeVar (template )
• • • Type (Covariant, inheritance)
• • • Optional
• • • Union (Variant)
• • Iterable
• • Iterator
• • Reversible
• • Supports__
• • collectIons.abc
• • ContextManager
• • Any
• • all-type
• • annotations (dict of type hinting)
• type module
• • get frame/global vars
• • co_xxx
• type<->object relation
• type hinting
• tuple
• • (1, 2, [3, 4])[2] += [1, 2] -> error + (1, 2, [1, 2, 3, 4])
• • check is after the assignment

U

• User data-type
• • inheritance from
• • avoid c-api (list/dict) error

V

W

• warnings module

X

Y

Z