Skip to content

Latest commit

 

History

History
218 lines (157 loc) · 6.55 KB

Function.md

File metadata and controls

218 lines (157 loc) · 6.55 KB
Raw

Function

1. Define

def fuction(argument(, argument)*):
    ...

1.1. Annotate Type

  • Annotation is expressions associated with indicated parts of functions
    • Stored as a dict from anntated parameter string to annotation expression
      • <Function>.__annotaions__ == {'<Parameter>': <AnnotationExpression>, ..., 'return': <AnnotationExpression>}
  • Annotate argument's type: argument: <Type>
  • Annotate return type: def fuction(<Arguments>) -> <ReturnType>:
  • Function with type annotation:
def <FunctionName>(<Argument>: <Type>(, <Argument>: <Type>)*) -> <ReturnType>:
    # ...
  • Annotation is prefered over type docstr

2. Parameter

  • Pass Reference, not Variable
[Original Variable] -> [Object]
[Parameter Variable] -> [Object]

2.1. Optional Parameter

  • Define: <Argument>=<DefaultValue>
  • Can provide value optionally when invoke
def function(argument=<DefaultValue>):
    ...

fuction(argument)
fuction()  # Equivalent to fuction(<DefaultValue>)
  • <DefaultValue> is a expression, and evaluated when the function defined

2.2. Keyword Parameter 关键字参数

  • 在调用时通常按名称指定值: fuction(argument=value)

2.3. 指示形式参数

  • 在定义函数时, 有以下两种特殊的指示形式参数
    • /: 之前的参数只能通过位置参数指定值 Positional Only, 不能通过关键字参数指定值
      • 名称不重要且总是以固定顺序指定值的参数可限定为仅限位置参数指定值 Positional Only
    • *: 标志可通过位置参数指定值的参数的结束, 之后的参数只能通过关键字参数指定值 Keyword Only, 不能通过位置参数指定值
      • 名称重要且有助于使函数调用更可读的参数可限定为仅限关键字参数指定值 Keyword Only

2.4. API Notation

  • []: 其中的参数是可选的

3. Object

  • Function is Function Variable
    • Function is Variable which refer to fuction object
    • E.g.:
      • def function()
      • function is a variable
        • Refer to a function object
  • Function Variable is Function
    • Function Variable can be used as Function: function_variable()
def original_function_variable():
    ...
new_function_variable = original_function_variable
new_function_variable()

4. Built-in Functions

4.1. input()

  • input(prompt: str) -> str
  • Print prompt without additional ending then read from stdin and return as str

4.2. print()

  • print(object(, object)*[, sep=sep][, end=''][, file=file][, flush=True])
    • Print object to file, separated by sep and followed by end
    • object: If is str, print as is; if is not str, print str(object)
    • sep: Default to ' '
    • end: Default to '\n'
    • file: Default to sys.stdout
    • flush: Default to False

4.3. all()

  • all(iterable) -> bool: 内置函数, 当iterable中所有元素都为真时返回真, 否则返回假
  • all(expression_list: iterable) -> bool
  • all(<ListComprehensionWhitoutBracket>) -> bool
    • E.g.: all(expression(element) for element in iterable)
  • Return True if all element in expression_list is True, otherwise False
    • Short circuiting: Terminate on first False
    • True if iterable is empty

4.4. any()

  • any(iterable) -> bool: 内置函数, 当iterable中任意元素为真时返回真, 否则返回假
  • any(expression_list: iterable) -> bool
  • any(<ListComprehensionWhitoutBracket>) -> bool
    • E.g.: any(expression(element) for element in iterable)
  • Return True if any element in expression_list is True, otherwise False
    • Short circuiting: Terminate on first True
    • False if iterable is empty

4.5. sorted()

  • sorted(iterable, *, key=None, reverse=False) -> List
  • Argument
    • key: KEY(ELEMENT: object) -> int
      • Function extract sort key from each element
      • Sort with lambda function: lambda <Element>: <SortKey>
      • E.g.:
        • sorted(['a', 'ab', 'abc'], key=len)
        • sorted(['a', 'ab', 'abc'], key=lambda string: len(string))
    • reverse: bool: If sort reversely
  • Return a NEW (default ascending) sorted list from iterable
  • Stable

4.6. max()

  • max(iterable, *[, default=obj, key=func]) -> value
  • max(arg1, arg2, *args, *[, key=func]) -> value
  • Return largest item
  • Argument
    • default: Object to return if provided iterable is empty
    • key: key(element: object) -> int
      • Function extract sort key from each element
      • Sort with lambda function: lambda <Element>: <SortKey>

4.7. callable()

  • callable(object: object) -> boolean
  • Return if objcet is callable

4.8. hasattr()

  • hasattr(object: object, name: str) -> bool
  • Return True if object has attr name

4.9. getattr()

  • getattr(object: object, name: str(, default: object)?) -> object

4.10. setattr()

  • setattr(object: object, name: str(, value: object)?) -> object

4.11. isinstance()

  • isinstance(object: Object, classinfo: Class) -> bool
  • Return True if object is instance of classinfo

4.12. issubclass()

  • issubclass(class: Class, classinfo: Class) -> bool
  • Return True if class is subclass of classinfo

4.13. chr()

  • chr(char_unicode_code_point: int) -> str
  • Return str character of given character unicode code point

4.14. ord()

  • ord(char_str: str) -> int
  • Return character unicode code point of given str character

4.15. reversed()

  • reversed(Iterable) -> Iterator
  • 返回一个逆序迭代器

4.16. abs()

  • abs(number): 返回number的绝对值

4.17. open()

  • open(file, mode='[rwxabt+]', buffering=-1, encoding=None, errors=None, newline=None, closefd=True, opener=None): Open file and return a corresponding file object
    • mode
      • r: Read (default)
      • w: Write
      • x: Exclusive write, failing if file already exists
      • a: Appending
      • b: Binary mode
      • t: Text mode (default)
      • +: Read & Write
    • encoding: Usually 'utf-8'
    • Returned object
      • Text mode: io.TextIOWrapper
      • Buffered Binary mode: io.BufferedReader, io.BufferedWriter, io.BufferedRandom
      • Unbuffered Binary mode: io.FileIO
      • seek(OFFSET, whence=(SEEK_CUR|SEEK_END)) to move cursor
with open(r'<FileDir>', r'<Mode>') as <FileObjectName>:
    # ...

4.18. vars()

  • vars([object]): Return __dict__ attribute for object (default to local scope)