python 3 妙招筆記

1. 換值操作

不再需要中間變量

>>> x = 3
>>> y = 5
>>> x, y = y, x
>>> print(x, y)
5 3

2. 顯示所有內置函數

>>> dir(__builtins__)
['ArithmeticError', 'AssertionError', 'AttributeError', 'BaseException', 'BlockingIOError',
 'BrokenPipeError', 'BufferError', 'BytesWarning', 'ChildProcessError', 'ConnectionAbortedError', 'ConnectionError', …… ]

3. 顯示當前工作區間內所有變量

>>> dir()
['__annotations__', '__builtins__', '__doc__', '__file__', '__loader__', '__name__', 
'__package__', '__spec__', 'guess', 'temp', 'x']

4. 顯示函數幫助信息

>>> help(dir)
Help on built-in function dir in module builtins:

dir(...)
    dir([object]) -> list of strings
    
    If called without an argument, return the names in the current scope.
    Else, return an alphabetized list of names comprising (some of) the attributes
    of the given object, and of attributes reachable from it.
    If the object supplies a method named __dir__, it will be used; otherwise
    the default dir() logic is used and returns:
      for a module object: the module's attributes.
      for a class object:  its attributes, and recursively the attributes
        of its bases.
      for any other object: its attributes, its class's attributes, and
        recursively the attributes of its class's base classes.

5. 字符串加法和乘法

加法爲拼接，乘法爲重複

6. 比較運算符

6.